Verizon will typically replace your phone with another if:
You are still under warranty, factory or extended
You have had at least 3(ish) replacements already.
Getting their online customer service involved finally got me over the hurdles with the Droid 2 a while back. I kept getting "certified refurbished" broken crap. One had missing keys, the other had a bunch of bad pixels, the other got so hot I thought it would catch fire.
Finally after those 3 they sent me a Samsung Fascinate. Great phone, but I knew Samsung was terrible with updates(at the time), so I walked into a store and paid $35 for a Motorola Droid X. The X was a great phone, wish I had just gotten it to begin with.
Either way, if you want a new phone that's going to be better but not screw you out of an upgrade, buy one on ebay. I bought my Bionic(in literally perfect condition) for a reasonable price. I'm now ready to get either a Note 2 or HTC DIx once it's released.