if you like flight sims and want to see what ac3d can do go here:
http://www.targetware.net/
we've sort of pushed ac3d over there cause its so easy to use. Many models has used it to build planes. I'm one of two 3D modelers that is working on the WW2 pacific game that uses AC3D. The F6F, P-38, Ki-43, Ki-61 (not yet released to the public) F4U, SBD, TBF, P-51, A-20s, and F4F was all made using ac3d. The programmers has added native ac3d support (.ac format) where we can just save and see planes in game. Not to mention that tons of ground objects and the WW1 crew use ac3d.
I'm about to start a tut on making planes in AC3D from scratch and some people might like to see it. the plane i'm making is a DO-17 and it should start showing up on the forum there in a few days.
I've used AC3d to make stuff for Call of Duty, Battlefield 1942, Fighter Squadron, Targetware, and Strike Fighters: Priject 1, and some parts for Warbirds 3. (CoD, BF1942, and Strike Fighters needed MAX to convert to thier format)
if you have any more questions i'm your guy.