I was inspired by biotech's awesome shuttle pic, btw...

Looks nice. More context, though, maybe.

Speaking as a photographer, colour temperature will make a big difference to lighting, getting the focus point right is another, if the background looks too sharp then Serenity won`t look right in sharp focus

Looks good though, oh and don`t forget the shadows + motion blur (not too much)

Darin (Zol.)

Looks great to me.

I like the flying foliage, like leaves being blown around by the engine wash.

Nicely done! I've only had to composit a handful of shots for what I do, but have had enough experience to know that doing it right is really tricky. The only thing I would add to Zol's comments would be about your contrast range within the image. The folliage is fairly contastry, with a lot of areas falling of into a dark dark grey. The butt end of Serenity is a little to bright compared to where it feels like the light source should be coming from. It seems like the background plate was shot during either early morning or late evening due to how much is falling into shadow. Maybe make your lights on Serenity reflect that low in the horizon light source and go a bit more contrasty with your fill sources?

Really nice work though! Thats cool stuff. What are your rendering/compositing in?