They are tough, but yes, the hubs were crap. Tough in that the full floater axles are nice for what they are meant to do. Crap in the regards that mine leaked the diff oil out and sprayed all over my damn wheels. Messy and all I got from the shop that installed them was excuses. It's warn's fault, not the shop's, I was just pissed to have spent that much money and then have to clean my wheels all the time. They have taken much abuse and with my lower gears and locker, when I bent my axle tubes I stuck with the M20 over finding a new rear due to the investment.
I had the axle housing retubed, my bearing cups welded back on and a ford 8.8 shim kit put back in instead of the stock M20 crush sleeve. My M20 is now bullet proof, but really, I've never actually shot at it.
I have beat it over some serious rocks though, and it's held up well. I've seen YJs break detroit lockers where this old M20 just hammers through, FWIW.
However, they came up with some lock out stubs which replaced the hubs and genuinely sealed things up right and removed a lot of the slop (hysteresis) that the hubs put into the system. Sure, I had the dream of eventually flat towing, now I'll have to remove the stubs and put some sort of cap on it for that, or just remove the driveshaft. I'll probably just remove the driveshaft.