The way Perl does objects is definitely a mixed bag. OO Perl is flexible once you've climbed the learning curve, which implies that you have the commitment to get there. The strange syntax, however, is enough to scare a lot of non-Perl people away (and into the waiting arms of Python).

That, and $| side-effecting the currently selected file handle, are my two gripes.

Oh, and constants. The use constant kludge, which produces second-class constants that misbehave if you stare at them the wrong way, is a real pain sometimes.