Most people who -don't- like him... seem to be the same people who have some grudge against Friends...
I am in the camp of the people who hate Friends. Well, let's say that I never got the appeal. However I have like almost everything Perry did away from Friends.
Now, the mark of a good voice actor is when I can't tell who the actor is when I listen to them. James Earl Jones may be a great voice actor, but you know it is him as soon as he utters the first syllable. We all knew that Shrek was Mike Myers, Glenn Close was Cruella Deville (but she was a good Cruella). So, to that end, Perry did a good job with Benny. Until this thread I did not know Matthew Perry did the voice acting for Benny.
Also, when interacting with Benny, the acting led me to look for a peaceful solution* as I started to actually understand why he did what he did and I was willing to give him the benifit of the doubt when he told me his side of what happened. If the voice acting had svcked, I would not have felt any empathy.
*I only said I looked for the peaceful solution, I did not say I used it.