xscope is nice, its fast and the zoom is the best around but pound for pound Dolphin HD is the better of the two.
After reading this thread I downloaded Skyfire, xScope and Opera Mini. In terms of speed Opera is the winner and it's not even close. I'd love to use it as my main browser but I don't like the idea of them storing my various passwords.
The only thing I don't like about Opera's UI is that the pinch to zoom doesn't zoom in far enough. Sometimes I like/need to zoom in really tight and Opera won't let me do that.