I tried ultimate, and thought I would really like it, but coming from basketball background, ultimate was too big of an adjustment for me. Peace-loving ultimate people were getting pissed off at me for being too physical -- boxing out and trying to rip the disc out of their hands and elbowing for position and so forth -- just natural stuff for basketball. But I found it was difficult to avoid falling into those habits, having played hoops for many many years. Maybe more serious ultimate players are OK with a little physical play, but the games I got in were way too non-confrontational for my taste.
F or people coming from other team sports where the players are mixed on the field (not volleyball or baseball), the biggest adjustment is the playing style that you talk about. No double teaming the thrower, no straddling the thrower's pivot leg, and other rules that you should learn (there aren't many). You also have to watch for people who take advantage of the rules (e.g. taking that third step after the catch so you can clear the defender). You also need to change some of your instincts - if you are back on a 2-on-1 you can ignore the guy who catches the disc because he isn't going anywhere - you need to stay with the free runner until you get some help. It is self-refereed and most guys honor the rules. The physical part is usually in the end zones when you have multiple players vying for the final catch/defend. That's where you get a lot of collisions and also get to show off your ballerina moves. And yes, gratuitous diving to make catches is a badge of honor.