I've had my Droid X 10 days now (Since release day).
I've already developed headphone jack issues due to a loose or faulty headphone jack. Random crackling, level loss and left or right side loss. Additionally, the static on the line is so bad at times, that is is randomly activating Voice Command, and Redial on the phone.
I've confirmed that is isn't my line equipment. 2 Headphone sets (1 New), 4 extension cables (2 new), and to top it all off... it has gotten so bad that today it activated voice command just from the jarring of going over a parking lot speed bump at the Verizon store.
Now I admit.. I use the headphones alot... I walk 2-3 miles a day, plus 4-6 hours at work with headphone on, so I'm probably just early to report this problem, but hopefully it's a one off issue. Also FYI, I carry the phone loose in a pocket and not in a belt case, so the headphone plug is exposed and potentially subject to some minor flex a lot of the time.
This problem was not evident when I reecived the phone, it took 4 days before I noticed it the first time, another 3 days to realize it wasn't the cables, and then another 3 days to get unbearable. (I've pocket dialed my last call 10 times today total, and had voice command activate 20+ times, all due to static on the headphone line)
The good news is that Verizon does have some warranty replacement phones ready for 2 day ship, even though new orders are now scheduled for 2 weeks out.
Another good thing is that it took all of 5 minutes in a busy store to get (seemingly) bumped to the front of the line when they heard it was a DX problem, and then less than 5 minutes to get the warranty replacement order placed and walking back out the door.
Just putting the problem report out there..., FYI.