Just watched it... I have to say that it wasn't as bad as I was expecting--but I was expecting it to be worse than you can imagine, so that isn't saying very much.
We'll start positive. There were some things that remained intact. Roshi is still a pervert. He takes any opportunity to grab Bulma, just like in the manga. >>; Goku doesn't transform into a deformed half-dragon in a Holloween mask, he actually does turn into an ape monster thingy. This form is called Ouzaru, just like in the manga, but he doesn't become massive. Yamucha is still a bandit.
The bad aspects will mostly be what you'd expect. Crappy, cheesy effects. Crappy acting--especially by Chatwin. Everyone seemed to be thinking the same thing while filming: this movie sucks. And it shows in their performance. Most of the actors give a half-assed attempt at trying to play their roles. Ever tried to play a game based on a movie and everyone sounds like they're bored? Yeah... There's a lot of that in this movie. In the movie, Nameks are considered a hostile alien race. Piccolo was certainly hostile, but not all Nameks are. Even though Goku transforms into an ape, like he's supposed to, it still looks like all they did was put him into a Holloween costume. The effects for ki are really cheesy. And...the Kamehameha can heal people? I don't think so. All the Kamehameha does is blow crap up. That's it.
I'm glad I downloaded this over going to see it in the theater. I would have wanted my money back. Not even being a Dragon Ball fan would make me want to see this movie again.