The 150 player JO servers are probably run by Novalogic. I played ok with 140 players with my old Barton + 9800 Pro rig. Certainly not as smooth as a 32player game but was fine for me. I just dont like the maps that are played on the 150player server, though some of the small ones are obviously complete chaos. A potential for a very fun game some of the time at least, so I'm glad they weant with such huge max players.
Can't believe ET:QW is only 24 players!

I'm looking forward to that game and TF2 the most.. but I've always been more of a fan of a bigger game, like BF2 maps are large so I play the 50-64 player ones.
edit: Someone mentioned Far Cry before to me as like 128 players?? Or something a little less? But I haven't heard a damn thing in years about that game in regards to multiplayer, so I'm guessing it doesn't matter if the MP sucks or if it was just too laggy for large #s of players.