Yea basically its all about the rubber compound, they are harder, a good bit, and they can develop flat spots but thats no big deal at all i hardly get any with mine and If i do they go away very quickly. I run them on my Daily driver tow rig because they are the perfect agressive tow rig tire IMO. They are very stiff compound so they don't bulge when you load em down and they last a good long time on the pavement. I had some 35" BFG AT's C load range and they sucked they would bulge like crazy when you loaded em up. Plus another benifit of the hummer tire is they give me an agressive enough tread to be able to get in a kinda sticky situation and not worry bout getting stuck where a stock towrig with all terrain would. And of course best part is price.
Granted they arnt gonna do as well as say a irok/tsl/other heavy treaded off-road tire would but they arnt made to do all that. Most people buy them expecting way more outta them than they should simply because they are "hummer tires so they should be bad ass"
Remember hummers are heavy as fawk especially with the armour plating so they have to have the stiff compound.
All in all i say its a good tire, but don't buy them unless you realize your buying an agressive all terrain tire, not a full out mud terrain tire.