I saw it last night and I thought it was alright. I really enjoyed the casting, acting and story. I even liked the kid who played Spritle, but going in there I thought I was going to hate him. However, I really didn't like all the futuristic CG outdoors settings. It was really distracting and took me out of the experience. I didn't really like the races either, which is strange considering I was able to enjoy a "Speed Racer" movie without enjoying the races.
It kind of sucks about the box office though since this movie was supposed to "test the waters" for future anime adaptations. Which I don't think would be true. I think that the overall perception of "Speed Racer" is something that has been changed from the original source material to something else. I believe that when people think of "Speed Racer" they don't think of the anime the anime genre that starting popping up around the late 80's/early 90's. They think of the aspects of the dub which have been transformed into a little piece of Americana.
Don't get me wrong though. Maybe it is better that studios aren't going to be picking up dozens of anime/manga licenses all willy-nilly now. But we still have some more to go with Akira, Robotech and GITS, which I think will be a better indication if anime/manga adaptations will be accepted by the mainstream American audience.