Yeah, the arena based field system is kind of cool. At least you get a choice of 3 or 4 arenas per map. I remember having an idea sort of like that a while back. lol, I wanted to even have like an arcade you could go to between rounds to kill time if you got eliminated.
Only problem with the multiple arena system is that everybody wants to play on the tiny airball fields instead of some of the nice, elaborate woodsball fields. There's one map with a pretty sweet woods field but we could never get more than 2 or 3 people on it. Didn't help that it was really buggy and sometimes people would spawn in the field that weren't actively on the player list and couldn't shoot or be shot. :\
The leaning system is very similar to what Calrathan and I had discussed when we were considering making a commercial game -- analog control for leaning and crouching. After a few rounds, I gave up on using it, though. It's a lot easier to just run around and shoot people.