*nod* I get a lot of questions about tilling in the woods. Why I wrote a whole chapter about it ...ummm....in another place available someplace else
Basically, I went with the Bronco size tiller (one up from the baby I think) of the Troy Bilt line of rear tined tillers. Rear tine is a must and I've always had Troy Bilts and wouldn't have anything else really.
This tiller is light enough that I can pick it up and put it in the truck (though not as easily as it was a few years ago ) and it cuts about 14 inches or so. Because of the softness of woodland dirt in normal weather conditions, I only make the depth about 2 inches and it will sink in a little deeper and give me a bed that is maybe 4-6 inches deep if I go over it enough times.
I just basically go over bigger roots and rocks. Smaller roots I chop out with a madock and stones I can get out I do, otherwise I leave them. The rear tine forward-rotation is a must in the woods. That way, as long as you don't try to force the tines down into the dirt, the back just bounces up when it hits something. A reverse rotation would catch on everything I think.
I tried the small Mantis type tillers and they take forever. This little tiller is the best $500 I spent for my growing business.
Here is a link to the Troy Bilt page for the Bronco. I should also note that this is the smallest one they make that has a reverse...which is huge in the woods when you find yourself right up against a tree.
http://www.troybilt.com/webapp/wcs/stores/servlet/product_10001_14102_91362_54971_-1
Edit: I just noticed that it says that tiller now has counter rotating tines...that wouldn't work in the woods at all I suspect. There might be another model out there.