Excellent first piece.
One thing you want to look at is the subpatching on the front wheel. Whilst the main surface is smoothed, the ends are not. Remember that only 3 and 4 point polys can be converted to subpatches, so take each of the end polygons and bevel them in until pretty close to the center then delete them and fill in the gap with manually created polygons.
I've put together a quick page to show you what I mean:
http://www.medwards.dsl.pipex.com/lightwave/cylinder