I recently changed from a Droid 2 to the D3 and have yet to supply any sort of protection yet. I personally recommend the Invisi Shield. Although pricey, they come not only just for screens, but they will do a front and back cover and guarantee no damage after removal. They are quite a bit more expensive than standard plasticy ones you'll get from your service provider, but in my experience they are well worth it. They have more of a rubbery texture yet don't restrict and screen interactions. Also, any scratch that may show on the protector will simply wipe away, and unlike standard protection, any invisishield stand will replace it free if it starts to peel or malfunctions in any way. Or if it feels like its getting old, they replace them for $5 a side ($5 for the screen, $5 for the back if you get that package).
Truly, I prefer the Shield over any case being that cases heavily restrict any top row on physical qwerty devices, they also collect sand and dirt in the nooks. My Droid2 was Shielded for the entirety of its life and looks bran-new underneath, minus the corners of course. And as an added bonus, they will professionally apply it to your phone at the stand free of charge.
