Whoa man. I'm sensing there's an undercurrent of drama here, but as I don't really know any of you, didn't play 5W and don't have a history of any kind (positive or negative) with the 100 MUSH's staff, I'm going to avoid stepping into that and just comment on my experiences, which have been overwhelmingly awesome.
It's now officially been two weeks since I joined. This is my first MUSH, and aside from @dev, who's as new to the style and community as I am, I've never (to my knowledge) played with anyone who plays this game before and have no OOC contact. I missed the important landing event and did not become involved until 3 IC days after it. Despite this, everyone has been immensely welcoming, I was readily involved in an ongoing social scene the second I was ready to venture IC from chargen, and I since feel like I have been warmly accepted as an equal part of the community and afforded all the respect and regard I could ask for. It took all of three days for people to start adding me to their relationship info on their wiki pages, plenty of people have sent me friendly pages indicating they like my character, and I received a flattering number of cookies in my first week. (They're kind of like anonymous little thumbs-up you can freely give to people you enjoy roleplaying with, which they see the tally of at the end of the week and help them earn 'luck' points to spend on rerolls and hero moments, etc.)
Are there cliques and characters with backstory tie-ins? Sure! But I have no problem with the way they handle themselves in this MU*. A prominent example would be the 'Tesla Three', which consists of Fiona, Martin and Lip, whose backstory tie-in is that they staged a social justice protest on the Ark by chaining themselves to the doors of the Tesla Station, resulting in them being incarcerated for treason. (Currently all characters in play must be juvenile delinquents, as it's part of the setting.) I find their backstory to be a compelling and interesting plot-hook, which I've regularly brought up IC when talking to/about them. I've interacted with all three characters, both as a group and individually, and though they definitely have a clique thing going, it is not exclusionary or detrimental to the setting, but quite the opposite.
Some players, though they are few and far between, can be a little standoffish and may require a scene or two before they start being friendly. I think this is normal, and it doesn't bother me; there were plenty of other people to interact with, and once I'd gotten my foot in the door (which didn't take long), they were as inclusive as anyone else has been. I would advise new players (on any game, not just this one) not to be discouraged just because a few people take some warming up to.
The game is packed full of excitement. Almost too much, as some people have pointed out, but I have to hand it to staff for how evidently they put their blood, sweat and tears into the stories they craft. The action moves fast, which suits me better than slow, dull social RP settings I've played in the past, and something new, intense and meaningful happens nearly every single day. The 'lack of threat' which @Admiral has pointed out, in the sense that characters are unlikely to die unless their players want them to, doesn't bother me. People have been captured, attacked, injured, threatened and run for their lives. The adrenaline factor is real, even if only NPCs die. That the emphasis is on how our stories develop around danger rather than just having a bloodbath and killing off PCs suits me fine.
I think it's a little disingenuous to say that you don't have to have watched the show to play this game. You probably don't have to be up to date with the entire series, but I do think that watching just the first episode provides a lot of background information for the setting which would help new players. I also think that whether you've seen the show or not, if you aren't apt to like it, you aren't going to like the MUSH either. The theme is survival in a post-apocalyptic world; it's gritty, intense, political, raw, occasionally violent and occasionally with smatterings of angst. There is moral complexity, and your character will eventually get blood on their hands, directly or indirectly, whether you like it or not. They will have to make tough choices. From an observation, I think the players who are having the best time on the MUSH so far are those who are embracing the theme fully and placing themselves at the midst of the action, at risk of such choices, rather than just faffing around camp. There's nothing wrong with faffing around, I just think that if that's you, you shouldn't be surprised if you don't have as much fun.
The staff know what they're doing on a level that intimidates me. Coming from a long line of MUDs with coders at the helm (and even staffing in one), I am now fully convinced that having storytellers at the helm is the only way it should be. They have the creative freedom to offer a lot, to everyone, and in processing my application, they were nothing short of helpful and patient in answering questions and asking me to make a few minor tweaks. I have thus far found them to be 100% transparent and open about how everything works, who they play, what powers they have as staff and what they don't. The system they employ to aid in action scenes, FS3, is good, clean, hassle-free, and very easy to learn and understand after ten minutes maximum of bleary-eyed confusion. I haven't used it before, but would again. I will also add, in staff's favour, that they seem to not be batshit crazy. I think this bears mentioning because it's a rarity in roleplaying communities, and I want to make it clear that when I say they're friendly and helpful, I don't mean that as a euphemism for 'overbearing and neurotic', which it very often is. A+ for staff sanity and approachability.
I'll touch briefly on the point about staff PCs stealing all the action: Yes, Grey (Orion/ @Seraphim73) is a central character. But I don't think he's more central than Cole, Quinn and Fiona, neither of whom are staff-played, to my knowledge. I'll admit that I sniffed a bit when I saw he'd had a bunch of scenes with the Grounder prisoner and then a lot went down before anyone could process, especially since it involved learning that the Grounders speak English and that Mountain Men exist. I would have preferred for that to be a lot more drawn out, and less centred on such a small group of characters interacting with the prisoner. I'm also sad that such major reveals were made before the moment of maximum tension (e.g. when the Mountain Men actually show up to abduct us). But I think they did a good job of rectifying it when they came back the next day, more action happened which they involved many more people in, and though he got the spotlight for one scene, I don't feel like I was excluded from the overall arc. It also just so happens that Grey is a terrific character by a terrific roleplayer. He's engaging, inclusive, writes well, has a thematic backstory which he plays to consistently, and he makes a point of acknowledging other people's backstories as well in his RP. I've enjoyed his involvement in every scene I've had with him, so it really doesn't bother me that he's a central character. With the exception of that one thing with the Grounder prisoner, his centralisation has been an organic result of his interaction with other players.
There is only one thing so far about the game that I really don't like: I think the senate is a silly idea. It doesn't fit the theme, will lead to plot marginalisation and will favour those playing mature and responsible characters. While I have no problem with mature and responsible characters existing, as they are necessary counterpoints, most of us are playing teenagers enjoying their first taste of freedom the way your average teenager would, and so the counterpoints are a little less thematic, even if it's necessary to have exceptions. Even Clarke and Bellamy aren't official leaders in the show, and they aren't universally liked. They just end up leading often because they raise good ideas, and I would prefer it if the 100 MUSH also just allowed leadership to organically flow towards whoever ends up having good ideas in the moment. We're teenagers, after all. And while it's been said this is the result of IC talks, they're IC talks that I wasn't privy to, and don't think the majority of NPCs would be privy to or support. The senate idea's also been given staff support for voting, so it's a little beyond that now.
Anyway. Play the 100 MUSH. Involve yourself in +events, they're a great way to get your foot in the door and be a part of the action. Wiki and +sheet-stalk people during your first scenes with them so you know which plot-hooks to raise, just like when you bring up the Summer they spent in France as a talking point with a Tinder date. And, uh... haters gonna hate, I guess. ¯_(ツ)_/¯