Walt Mossberg says that it's much better with phone calls than AT&T but the data speeds are shorter.
Josh Topolsky at Engadget pretty much says the same thing, offering some charts for data flow that indicates Verizon is a lot slower. But Topolsky also says that it's probably not something you would notice in your day to day puttering around town. He also says that the battery life is a lot better.
Both Topolsky and Mossberg flag the unlimited data plan as a plus for Verizon.
Here are a ton more but the theme is pretty much the same: