Unfortunately, so many things worked against the title for me, that I'm not a fan.
Granted, since I'm a fanboy, I had expectations. And they were dashed.
The fighting is frustrating, it devolves to button mashing that's not even fun (like Soul Calibur is fun), feels unpolished (art to animations to transitions to performance), the dialog and expositions are stilted and heavy-handed, and it just didn't do it for me.
Now, that said, it is fan-fare -- So I dig seeing my guys and gals in tights in a new setting. And while the characterization and dialog is challenging for the most part, a lot of love was obviously spent just on the Joker -- and he comes across well. There is one cut-scene moment Joker reaction when the main baddy is announced that is money, and makes the whole game worth it. Actor Richard Epcar doesn't take the place of Mark Hamill's joker for me, but he sells it.
The other thing to note is I played the whole thing on the Xbox 360 using standard controllers, and the 360 D-pads are crap -- especially for fighting games.