I'm new to the forum, but thought I'd share these experiences...
I've purchased several different 'Droid X' cases and chargers from sellers on ebay. Here's what I've found...
I tried 3 different jelly 'skins' and all seem to be ok. Didn't have any problems with any of them. I tried 2 different 'pouch' style cases with belt clips. My advice here is to either buy the cases from Verizon, or find cases that are truly designed for the Droid X. Both the generic cases that I got had magnets that hold the cover closed. Due to the placement of these magnets, when you put the phone in the case face-forward, the phone thinks it's installed in the multimedia dock, and the display stays on. When you put the phone in these cases facing backward, the phone thinks it's been installed in the car dock. Both the display and GPS come on. Also, these cases have no holes where the top button is, so whenever you move, the button gets depressed, and the display quickly toggles on and off... and doesn't stop until you remove it from the case. Battery life with the phone in either case I bought was about 90 minutes. And the phone got *hot*.
I bought 2 AC chargers from different vendors. Both worked fine. Both were rated at 650mA. They actually charged the phone fairly quickly.
I bought 2 micro-usb car chargers, and neither worked. Well, both of them *worked*, but neither of them would charge the phone.
One actually acted as a trickle charger and charged the phone from 50% to 60% in an hour. Charging with the 2nd charger didn't show any additional charge on the phone. On the other hand, the phone showed the same charge that it had when I started, so I guess the charger did prevent the phone from running from the battery. Both were rated at 450mA (said so on the box, anyway.)
All of the charger tests were performed without making any calls, and with the display off.
I'd recommend sticking to chargers labeled as 'rapid chargers' or 'quick chargers', as these typically have higher output. The charger from Verizon (the one with the USB port on top) will charge the phone from 50% to 100% in an hour or so if you don't make any calls and don't use the display.