I've ran my 37"s on the road very little to and from the trail head. What road time they have seen has been fairly pleasent. Pretty well mannered tire on the road and as others have said very quiet in comparison. Off road probably THE best all around tire I have ever used. They work great for normal trails and are awsome in the rocks. They also perform well in mud and snow.
I agree with what others have said, even with the harder compound tires, you are still looking at a very soft grippy tire, constant street use will kill them in short order.
Just to clarify there are or were 2 different compounds Red, ie. Drag slicks with lugs. And Blues, More along the lines of a Drag radial with lugs. I have the blues, most comp guys run reds.