There have been a million threads on cases, but I'm going to chime in here...
I have the iSee, which is nice, clear acrylic, hasn't scratched anything, adds a little extra to the phone. It's a nice tight fit, so, it's a pain to take it out and dock it to charge. Wasn't really a problem cause I could charge it with the cable with the case on. Got the Apple Bluetooth Headset, and it looks funny in the travel charger and not in the dock.
I'm considering the SENA cases now. They look pretty good, and I love the idea of being able to dock the phone with the case.