I watched this at the weekend - a very faithful film of the graphic novel.
The art work is totally in keeping with the style, and while there are a few small tweaks, they are more an issue of tidying, I think.
For example, when the Joker kills the studio audience, in the film you do not see the Joker riding the dolls above the bodies, and there's no "Zex, zex, zex!" guest.
The story does have it's flaws, which show on the screen - for example, there must have been a few thousand rounds shot at the Batman, and only a single bullet hits.
But any flaws are simply due to a 25 year old story looking a little dated by the very media that were inspired by, and followed it.
So while it's good, it no longer seems quite so revolutionary in context with more modern Batman storytelling - heck, storytelling in general.