Okay,
You guys gotta check this out if you havent yet. Netbeans4.1 + Mustang + Netebans Profiler == one slick as heck profilign environment 
I’ve tried all the Eclipse profielrs and i gotta say IMHO this beats them hands down. Its about as good as OptimizeIt, but its free!
I was just about to search/post about which profilers people are using.
I recently tested out the NetBeans profiler and I have to say I think OptimizeIt was easier to use but since I no longer have access to it and it cost big $$$, I will using the NetBeans profiler unless someone thinks they know of something better.
BTW, separate from the profiler is the Visual GC tool and that is excellent, nothing else like it I know of (at least for free).
Together, they really give you some good views into what is happening…