Several people have stated that they have signal issues with the Captivate, and that the newer firmwares are helping with that quite a bit.
Crossing fingers, and looking forward to evaluating.
FWIW, I got an EVO 4G when they came out, as did several of my coworkers. I returned it because, though it was great at what it did, it wasn't as portable/pocketable as I liked.
But, I knew that FroYo (aka Android 2.2) would greatly speed them up, and I wanted to test it. it certainly ran Java faster, and seemed to be great. I returned the EVO, however, and picked up a Captivate for the graphics coprocessor and smaller physical dimensions.
Now, my coworkers are reporting that 2.1 was more stable. they have had crashing and lockup issues on the EVO since going to 2.2. Understandably, that's only four people. But, it is also 100% of my sample group.