I've just seen it!
I went in telling myself to keep an open mind so I wouldn't be disappointed if it was too different from the Astroboy I knew.
To my surprise, it took no effort to get into the story. I was not convinced about the 3D Astro yet, but it worked beautifully, with Astro having so much expression!
I didn't like some of the plot, but it was still much better than other superheroe stories like, say, Spiderman III. Overall I liked it better than the 2003 series, but I do agree that it could have been more interesting if Tenma had been more mad. If they make a sequel, maybe they could find a way to cast him into more of a bad guy, that would be nice.
Maybe with Atlas or the Blue Knight, who were nowhere to be found.
I enjoyed all the references to the other stories and Tezuka's world, like the bad robot getting bigger from other robot parts, the hyotantsugis (there was one that couldn't be missed at the end, but I believe I also saw one for a quarter of a second in the beginning), seeing Astroboy drawn more traditionally on the design sheet, Hamegg first presenting himself as a good guy, etc. It was full of references.
Even the robot Astro woke up reminded me a lot of The Wreck of the Titan.
As for the voices, I saw the French version. It was said in the movie that Toby was 13. I thought Astro's voice sounded cute enough that it never crossed my mind that he was too old. He sounded more or less like the 2003 Astroboy (unless my memory of the 2003 series is off). If Astro had a Quebec accent, I didn't find it really noticeable (our European friends will probably be better able to make that distinction than I am). On the other hand, Tenma must certainly have lived in French Canada at some point in his life!
It's no surprise that it was the actor's first dubbing experience, I guess.
I don't know how many people there were in the room. I saw somebody wearing a mask, but we were maybe only 20? There were a few adults without kids, and at this hour it's no suprise that there weren't too many people with kids. When Tenma took Toby's cap in his hands, the little boy behind me said "Toby est parti..." (Toby is gone).