I've been a sprint customer since 1998 and I have never thought of changing. Sure, the phone selection isn't as broad, but the interesting thing about that is Sprint carries many of the same phones as V/AT&T, and the usually get them earlier too. Seriously. And why don't most people know this? Because the model #/name used by Sprint isn't usually the same as used by V/ATT. Same phone, different name. I've seen this more than 20 times. Now, every carrier has their "flagship" phone so don't cry "But ATT has the iPhone" or something. Sprint has a few phones not carried by the others too.
My brother has V, my neighbors ATT and T-mobile. I pay much less for more, FASTER, better coverage service. I've never had a billing screw up even with three phones (used to be four) on the same account. Voice, data and text.
Sadly, where I live, 4G is a ways away yet. So I won't be getting an Evo. Not to mention my trusty HTC Touch is working fine for me. Exchange sync and all.