I kicked this one around before I signed up with Verizon and got the Inc. I could have waited a few more weeks to make my decision, but made it based on Sprint's ability to deliver 4G (not anywhere close to deploying in NYC from the looks of it), and their coverage overall.
I'm taking a wait-and-see. I signed a 2 year, but that's with a pro-rated $350 ETF. I can bolt halfway through for $175. I paid $99 for the Incredible , so it'd be like having paid $275 for it for a year, not bad (especially considering the resale value of the phone halfway through).
I'd take a look a year from now and see if the reviews on Sprint's 4G network are favorable, and make the call then.