I've been running 33x10.5x15 BFG MT's on Ecco wheels for about 5 years now. I'm on a RE 5.5" lift if that affects your comparison...
I rubbed on the leading edge of the front flares and the trailing edge of the rear flares. Minor trimming of the flares took care of that. They stuff nicely inside the wheel wells however as was mentioned above, they rub on the inner fender walls like crazy if you don't bumpstop properly.
That being said... as much as I love my Eccos, I'll be installing some Cragar V5's with my next set of 33x10.5's. I'm hoping they'll still stuff nicely but won't rub my control arms or the inner wheel weels so much.