I've been using a 72" Befco Tornado for about a year now. Does a great job on my 6 acre field, where I've been gradually turning it into pasture by mowing it often. The first few cuttings the mower hit some pretty good rocks, which put a few small dings on the sides, but it pretty much contained the debris and didn't send anything flying. I have also cut light brush - up to 2" - with no problems.
Mine has both shear bolts and a slip clutch... found out last week what it's like to snap a shear bolt on a hidden stump... I guess the slip clutch needs to be re-tensioned. My bad for not doing it when the mowing season started.
I would consider mine to be a light to medium-duty cutter, and it's probably on par with some of the other better units out there (Landpride, Woods, Bush Hog, etc.). Good welds, good paint job, solid components, runs quiet (except when Einstein here hits a rock or a stump /forums/images/graemlins/crazy.gif) etc. Would not hesitate to buy it again.