As someone who has never seen a Joss Whedon product but has heard generally good things about him, I demand that gaf explain to me what the deal is with him, good or bad.
As someone who considers most of his work some of the best pieces of entertainment I've seen I can't say much of what is bad (plenty of others will do that). What I don't like is half of Dollhouse, some of Alien Resurrection, and the original Buffy film. He and his fans will debate forever how much involvement and control he ultimately had with these projects. Sometimes I tend to give him the same level of credit that I give him with Toy Story. Which is very little, and other times he's totally responsible. The writer of Speed gives Whedon credit for much of dialog in that script, and the infamously stupid "frog lightning" line from X-Men is credited to him. The point is it's hard to tell which is really his and which isn't in some of these films.
Anyways what I like about him is the humor and unexpected nature of what he does with characters. Making you like people you shouldn't (airheads, villains etc.), killing off characters you love in fantastic ways, directing one of the saddest, most punch to the gut episodes of television ever ("The Body" episode of Buffy), and some really smart comedy writing.
Moments like these (they are short and humorous and require no knowledge)
Firefly #1
Firefly #2
Angel
and finally a line that he himself did not write (his brother did) from
Doctor Horrible.
Come at me Whedon haters!