Other than the plastic trigger and mainspring housing, I like the 1991A1. All things considered, it's the closest thing on the market to Colt's original 1911. Since the "originality" of the gun particularly appeals to me, I don't modify my 1991A1s. Of my three (.45, .38 Super, and 9mm), the only problem I've encountered was a weak extractor in the 9mm. Colt's service department repaired it.
Having said the above, it's my experience that 1991A1 quality is not consistent, although I haven't seen one that was really bad. So maybe part of the reason I've had good luck with mine is that I picked them very carefully.
YMMV.