Most upper-echelon Challenger players have at least one good spell in their careers
DGT is not a bad player at all, but he's not as earth-shattering as some people make him out to be.
That's true, but I'd consider DGT a lower-level ATP player instead of a higher-level challenger guy. I think he's done enough at the ATP level to be considered a legit ATP player and generally he does very well in challengers, he's above challengers, IMO. I do agree, though, that given he sucks about 70% of seasons, that he's not as good as some think he is, performance wise.