I base my reviews on my feelings, my thoughts and my enjoyment referring the specific series. So this is not a overly professional critic's review.
First off all, I bought this straight on DVD the moment it got released, so my experience with audio/subtitles etc. Can be a bit different then the people who watched it from fansubbers.
The fact that I bought it on DVD is because people who worked on the hitmovie, Akira, also worked on Steamboy for several years, noticeable from the drawing style.
We'll go right further with that. The animation in Steamboy is really amazing if you ask me, the steam itself, the fast scene's on the steamball and Ray's own invention are truly fascinating, I missed most of the original story, just to be amazed by the animation. (May this be a warning to people who love the work of animation)
The story itself is good too, in my opinion, I won't write a small summary here, since someone already took the liberty to add one to the series page, (probably somewhere above this review). The plot takes out pretty well, it's starts in an exciting way with an amazing escape and a chase throughout a part of the city and nearby fields.
As for the animation, the art's a big and important factor of animation and of course the movie itself. Most of the art was just like the previous project Akira, only improved. The characters were "standards" and yet unique for they're way of movement, talking and thinking. You won't be bored here, but you won't be too suprised either. The introduction of the characters is well done in different ways either, yet again, not to suprising scene's.
The sound (on DVD ofcourse) is set with a few options, DDS versions etc. Nothing new, but the sound's pretty good, the voice-actors, the machine sounds and most of the backgrounds music is really good.
I rewatched this movie several times since I bought it, and although it's highly enjoyable at start, the few times after it stays the same. For an anime movie, this is pretty good, I don't rewatch alot of animated movie's.
So there's a 9 for the story, 10's for the Art, Sound and Enjoyment, and an 8 for the characters. Which I calculate to a 10 overall.