I have about 1600 miles on the stock Metzeler Karoo's. I've run them at normal street pressure off road and haven't had any problems. I haven't done any extremely rocky terrain, but have done some deep sand and I made it without crashing, so for me that means they are fine. I don't notice the nobs on the street, and cornering is fine. I really like these tires, i just wish they lasted longer. I'm not a very agressive rider on or off road, so at most i'll probably get 1.5x the miles on these that most will. maybe double.
I was talking with the parts guy at sierra, and I think I'll move to the Metzeler Tourance Tires for the next round. should be perfect for the AK trip with tread to spare (burn) when I get back.
I was also talking to the parts guy about patching tubeless and he said best to carry a 21" tube. that will fit the front and can be crammed in the back if need be. you can get tubeless repair kit and can be used for the rear (he got 1500 miles on one repair) but warned against any use in the front. just not worth the chance. the tubeless repair kits say limited to 30 miles at 37mph so the disclaimer indicates they are extremely temporary.
at this point i'm kind of torn... I know I should carry at least one tube, but to use it that means i have to bring tire irons and possibly a bead breaker?. another unfortunate difficuly in the HP2 is the lack of center stand, so road side tire repair could be very challening. hmmm....... what to do.