There are good repops and there are bad repops. Here's a thread on that topic:
http://forums.maxperformanceinc.com/...d.php?t=669245
Edit: I found the pictures I took but not the article I wrote. Here's the most compelling reasons NOT to buy the cheap ones.
The studs are the wrong spacing and the shape is different:
This pic shows the difference in thickness, finish and stud length between the two:
The good ones are from Trimparts