I've been using a VV Gripper for about a month, bought it because of the $40.00 price from MV.
First one I received had to go back for replacement, could never get it to turn on - five clicks, slow, medium or fast, nothing worked. The display would flash when the battery made initial contact with the door, but never anything after that. MV replaced it promptly with no problems.
Second one, the one I have now, has worked quite well, no problems to report other than two occasions where the problem from the first gripper seemed to be happening again. I managed to get it to turn on both times, and have found that I can prevent this from happening by leaving it standing upright whenever I leave it in the off-mode for an extended period, usually overnight. Doesn't make any sense, I know, but leaving it laying on its side seemed to make this occur, again I can't explain this.
Battery door has not been a problem so far (knock on wood). If/when it does break, I plan on putting the electronics in a new box, and keep on keeping on.
I usually leave my gripper at home and use my MV VV box mod when I'm out and about, I built it last February, use it constantly through the day at work, and its still going strong - it truly has been a great value for the money.