I'll address each:
Terrible acting
Bullshit. Emile Hirsch is charming as hell as Speed. Hirsch played him as the cool, nice guy you want to know in real life. Seemed like a totally awesome kid. John Goodman is.. well.. John Goodman which is good! The scene where he argues with Rex as well as the mirror scene later when he comes clean with Speed... he delivers both with heart and charm. Susan Sarandon's "you take my breath away" speech was touching, giving the otherwise throw-away character of Mom Racer something to contribute to the film. Roger Allam was over the top but in a wonderfully delicious way. As has been said already in this thread, his bad guy speech is oozing with loathing and spittle. Loved it. Mathew Fox brings the most serious performance and while Fox was rather flat and wooden, it worked for the character. The rest of the characters we're alright but nothing special. Even the kid who played Spritle wasn't bad in a "Disney movie" fashion. He could have been much worse.
Annoying characters
Spridle and Chim-chim were indeed annoying at times. I'll grant you that. However, at times they'd win you back like when Spridle gave Royalton the finger and Chim-chim threw monkey-poo at Crusher Block. I could have done with fewer scenes of them but I assume that was to cater to the younger audience. All of the other characters in the movie were great (aside from maybe a silly villian here or there).
Cliche-ridden script
Dude... it's f-ing Speed Racer. The cliche was deliberate. It was a celebration of the cartoon's waky premise and ridiculous foils.
What were you expecting... Citizen Kane?!
Shallow
I don't even understand this complaint. The world The Wachowskis created for Speed Racer to inhabit is remarkably rich if you pay attention. It's much richer than the initial premise (live action cartoon) deserved. They created this sort of alternate history of our world where not only has car racing become the world's biggest sport but there's a real pro-environmental message hidden beneath the surface. Did you notice how clean everything was? Shiny? Did you notice all the cars were electric? Clean energy, clean society. The history of the WRL itself, described in detail by both Pops Racer and Royalton is quite rich. Not to mention, it delves into the darker sides of this society which revolves around corporate coruption and media control. Shallow? I don't see it.
Ridiculous premise
Again, it's a movie based on a cartoon. About the only thing rediculous about the concept when viewed within the world itself is how Royalton Industries and the other corrupt companies kept the secret for so long but... again... considering it's not to be taken TOO SERIOUSLY and is a fun family film I'll let them have it. Lighten up. I get the impression by these complaints you would hate a movie like Tangled for the same reasons.
Occasionally jarring effects
Bwhahaha! Uh yeah. That's like 50% of the charm of this movie. Those effects are so far out there. I can't even think of another movie like it. I love they pushed the envelope of camera moves, zooms and transitions to such extremes. It reminds the audience to sit back and enjoy the ride and not get too bent out of shape when silly, cartoony things happen in a movie based on a cartoon.
Running time too long
I can't agree. In fact, when I watched it again the other day it seemed the time flew by. The visit to Royalton Industries and the Ninja stuff did drag on longer than I'd had liked but all of the other scenes with their manic editing and creative intermixing of timelines was fast as hell. Just like... Speed Racer.
Is it a kid's film? Is it a family film? Is it an action film? No identity
It's a family film.
Not made by Pixar or Dreamworks
Talk about being shallow.