I can honestly say I wouldn't recommend the Amzer Rubberized Black Snap on Crystal Case (bought here:
Amzer Rubberized Black Snap on Crystal Hard Case For Motorola - Motorola MILESTONE - Cases).
I've had it for less than a week and the bit that snaps onto the screen has already wedged itself loose and won't snap back on again. I got it as a quick (and cheap) solution after dropping my Milestone and afraid of doing it again based on how clumsy I am. However, it really wasn't worth the money. And it actually looks a lot cheaper and is a lot more bulky in person than it does on the site.
I'm wondering now if I should just have a case to slide the phone into. Still not sure. I am definitely interested in hearing others people's opinions and experiences though.