I am marginally pro-OOC room, for one specific reason: I'm not someone who grabs a pile of friends to start off on a game. I usually go alone, even if I ask others to join me there after feeling it out, if I've decided to stick around.
A notable measure of 'how comfortable I'm going to be in a space' is seeing how people relate to each other OOC when not in a scene. Seeing that people are joking around and friendly in downtime is reassuring when shit hits the fan in a scene, and something dramatic or tense goes down in that I usually find it easier to engage someone (IC in potentially tense subject matter, or OOC if there is an issue) when I have observed them behaving in a chill, friendly manner with others in the playerbase.
There are obvious exceptions to this -- if they're only friendly to their in-joke circle, for instance, or only engage those people even when many others are present and chatting freely -- being the big one. The new one on me was someone going on effusively about what a great time they were having doing something that was making me utterly miserable, which made me feel like I could not approach them to say, "Yeah, your super fun times, please knock that shit off." It was a big problem, but it is also in that category of what I'd call 'rare exceptions', in that it's happened all of once in over 20 years.