Two Face was awful and Carrey's Riddler was big and loud enough that they didn't actually need a second villain.
O'Donnell was too old for Robin - he looked like a young man, able to lead his own life, not someone who had to be a ward of court. Having said that, his performance is quite good.
The humour is silly - not quite brave enough to go out and out wacky like the 60s show but out of place in a 1990s Batman movie. And worst of all, mostly unfunny.
The Riddler's plan is pretty much a re-hash of anything that's gone before in previous movies.
Too much marketing and toy manufacturing behind the outfits and vehicles. Also, I'm not keen on the neon look of Gotham, which is better suited to a Dick Tracy movie. But it's a legitimate choice for the movie-makers to have made.
The movie is probably too long.
Besides that - I actually quite like a lot of this movie. I'm in the minority that prefers Kilmer to Clooney or Keaton, the action scenes are way better than anything in the first two movies and I like Carrey's Riddler. Michael Gough is as good as always.