Two things killed the Nexus One for me:
1. Two versions of the device. I travel to the UK a lot and I wanted to pick up a Nexus One so I wouldn't have to unlock my iPhone. Being forced to choose between 3G in the US (on AT&T) or 3G in the UK made me choose neither.
2. Skype is a Verizon exclusive. Yay artificial fragmentation!
#1 can hopefully be fixed by the Nexus Two. Not so sure about #2.
#1 can hopefully be fixed by the Nexus Two. Not so sure about #2.