Do cell phones with prepaid plans lose the "goodies" that comes with contract phones?

I’m interest in unlocked phones, particularly the HTC HD2 and EVO. Both phones are advertised as unlocked at Best Buy. However, i’m wondering if I were to use them with a prepaid plan will I lose all the good stuff. It would be a shame to spend $600-$700 for a phone without being able to use all that it offers.

Contract phones has some plus points, but you won’t be missing much.
It’s best unlocked so that you can switch to other operator (home/abroad) easily.