DP 8.1 GDR1 works amazingly well on the Neo. However, due to Samsung's lack of initiative to push out the official firmware, GDR1 broke two main phone features. Nothing that can't be worked around but still irritating:
1. Either at the start or if you hard reset after the update (if you don't experience this DO NOT HARD RESET) the MMS apn is totally fried. Even if you enter it manually, no apn you try (at least for ATT) will work. So your phone cannot send or receive MMS messages anymore until Samsung gets off its ***.
2. This one is more minor and just causes device pairing issues. The name of the phone as well as the main ringtone will reset every time you turn the phone off and on. Creates hell for bluetooth recognition and it took me a while to figure this out after my devices were not pairing automatically anymore.
As well, sometimes your apn for internet will randomly delete itself. Re add it and it works fine again. Also, i've noticed some wifi will not connect automatically anymore. This is rare but it happens once in a while.