Had my Droid X about a week and the only two accessories I have purchased are the Ulra Crystal screen Protector and The Motorola car dock.
Steinheil protector is best screen protector I have used on any phone, previous being the Backflip and HTC Tilt. I used the recommendation I found on steaming up your bathroom to kill dust and it was flawless install.
The car dock opened up the X's voice navigation world to me. I first tried it a few days with the phone sitting on my console beside me. It was okay but had to tae your eyes of the road to do anything or look at map. I will not use it anymore unless it is in a cardock. It was much easier to use and the map was stunning, even in the bright sunlight in the interstate in Florida.
Hope this as helpful to some as all the info I dug up on these forums before I bought my Droid X.