I have only been using AC3D for a day now and I love it. There are a couple of things that would make my life a lot easier.
I could
really use a background image in the 3D view, one that works just like the background image in all of the ortho views. I do a lot of work from photographs and sometimes you just can't get an ortho-friendly shot.
I also model a lot of symmetrical objects, cars and such, so if the previous poster is correct and there is no "mirror" function I'd like to see it added.
Additional ortho views would be nice. It is sometimes useful to work with front, top, back or similar combinations. Three windows at a time is fine (IMHO) but it would be nice to be able to choose what view goes in what window.
Down the road I would really love to see CgFX (
http://ww.cgshaders.org/) support so that I can apply a custom shader at modeling time. I haven't looked at the SDK yet but I'm hoping I can add this myself if necessary.
Great program, happy to pay for it.