The first game I played on in a MU format (not counting AOL games using Private Chat rooms with names of the location etc) was Anomaly Trek MUX which had a pretty detailed map for the station and some smaller ones for key ships -- and then removed ones for particular planets and a frickin' load up a desc for a place and store it holodeck system I loved. The thing is, I walked that grid to go places, I never @tel'd if I could help it unless it was to Planet Hell where an ST'd adventure was going to be going down. I even avoided just using the home command to go back to my quarters unless I absolutely had to go right now, I'd walk the ring to the turbolift, choose my floor, head down to my quarters and then log out.
The next place was Denver -- and it had a pretty big grid, and it had Car bits I could drive around the grid with. I loved that. I had numerous scenes RPing with someone as we drove around the city from one place to another and then kept right on playing as we got out and went into the Chantry or whatever. Again, I rarely just jumped -- I went through the city unless I was logging on for a scene starting RIGHT NOW being run by someone else.
One of the things I missed on TR was the culture of actually traveling the grid (AND MY CAR). I ended up traveling the grid a lot anyway because it was important to me to know the layout of the City so I could RP better about it. It was good for me to say, Oh yeah, the Tapas bar is here, by this... but if you want the best clock shop, you can go over here by this and check that out.
I like lots of places available for me to go to, it helps inspire RP ideas for me, but I understand the benefit of Temp Rooms, it reminds of the Holodecks on Anomaly. If you only play with a few people in limited areas, a big grid doesn't matter -- but I like open world exploration and a grid full of people's creations give me a chance to discover things ICly and OOCly, and I frankly liked that. Not everyone is looking for the same experience on a MU, obviously, and I can deal with the view that smaller is better and quick travel is king... but I won't lie, if your grid is huge and insanely over built and full of vast amounts of places to go that perhaps see RP in them once a year, I would probably love it because that appeals to my sense of immersion, and for some reason the five to ten minutes it takes to make a temproom and the describe it breaks off my feeling of the flow of RP while in transit, and I like RPing through my world, not just moving from set to set.