I have a blackberry torch and like it. It doesn't require the extras that the iPhone does and is sturdier. It has a full touch screen and a slide out QWERTY keyboard. It also lets you read and view videos sideways, giving a "widescreen" view. I upgraded from the regular Blackberry Bold and it was an easy transition. In general I like the touch screen, though it does sometimes register my cheek touching the screen when I'm talking and put people on mute or try to "add a participant" to the conversation. It's not supposed to do that but I haven't had the time to call in and ask why.
I do recommend getting a screen protector for any smart phone you get though.
AT&T has many great smartphones, but the best out of all of them would be the Apple iPhone 4, Samsung Captivate, LG Vu Plus, Samsung Focus, and the Samsung Mythic. You can't go wrong with any of these phones, especially the first two.
There are a lot of good smart phones, but I would go with an iPhone. That's what I have and I wouldn't trade it for anything else. The only change I would like is that I wish it was a little smaller like some of the other smart phone. But hands down the iPhone is the way to go