I have a Droid X. Over the weekend I bought the Samsung Captivate (AT&T's version of the Galaxy S) for my wife.
I have to say, it's a really nice phone, but I wouldn't trade in my Droid X for it. It's quite stylish and very thin, but there are some design/UI tradeoffs that I don't like. My wife is nowhere close to being a power user or an Android enthusiast, so she's OK with the following:
- No LED flash.
- Samsung's TouchWiz 3.0 UI isn't great. As others have mentioned, it causes occasional lag and slowdowns on this phone despite it having a 1GHz Hummingbird CPU.
- AT&T has locked out sideloading apps on all of their Android phones. I'm guessing they did this to protect the user from installing potentially malicious software, but IMO they should at least give the end user the choice to disable sideloading or not.
Aside from that, the Super AMOLED screen is the one thing on the phone I'm truly jealous of. It's simply a great, beautiful display. Blacks are jet-black and looking at the display in a darkened room is a wonder to behold.
The other benefit the Samsung has is that it's got a whopping 16GB of onboard memory and comes with an empty SDHC card slot, so it's expandable to a total of 48GB of memory. That's phenomenal.
Overall, I would be totally satisfied with a Captivate if I had to stay with AT&T.