Same functionality but the advantage to the .56 was that it was an official release and considered stable by MTS. Thus far that is the ONLY one that was an official release.

All other releases including .66 and .77 are technically betas though conventional wisdom would think that they have less bugs though that may not be the case. I'm sticking with .56 until I see a compelling reason to upgrade OR Verizon finally releases an official release.