Ok - having been an avid fan of the cartoon for sooo long - I can tell you that I ADORED the movie. I felt that it did a great justice to the cartoon, and was a good representation of what live-action-animae would look like.
I felt that the movie was well cast, the actors pulled off what the characters in the cartoon were. John Goodman as Pops for example, was brilliant. Matthew Fox also did a good job of bringing Racer X to life (especially, since his face matched the relative profile also done in the cartoon.). I thought the representations of the cars were also brilliant.
Did they take liberties with creating this movie? Of course they did. But I feel that they kept with the spirit of what Speed Racer is.
To the naysayers - all I'm going to say is, let's agree to disagree m'kay? I know there are people that feel you can get the same sensation by tossing a bunch of lightbulbs in a clothes dryer and get the same effect. That is their opinion - and that's ok..rilly.