HTC Sensation 4G (T-Mobile)

Pros: Big screen, rapid responsiveness of apps + 4G speed

Cons: So many features, so little battery to cover them all.

Summary: Definitely the best smart phone I have owned. My wife used the telenav feature while I drove and found her way on the UI easily, multi-tasked and proclaimed it "better than my iPhone." I have not owned an iPhone but replaced a Droid2 with the sensation and my life is definitely improved by the device. It is likety-split at loading and moving from app-to-app and the 4G speed in NY and SF has made an impressive difference.
Strong call and sound quality makes it a great phone and the feature richness has me leaving the other devices--laptop and iPad--collecting dust. I wouldn't change the slime size for a bigger battery but would like it to have more juice. I just have to be more vigilant charging, and it is worth it.