Not as touch sensitive as a Wizard for sure, but I find if you roll your volume back a bit it gets plenty touch sensitive. Full on they are compressed, but really not much more than a III, which i've owned. I think some people exaggerate the amount of compression in these amps, just listen to Lamb Of God's killadelphia DVD and you'll hear that it's a little more open sounding than some think. The Mark V on the other hand is beyond compressed, just really flat sounding.
Oh and Lamb of God use the Rev B heads. In all the studio pics i've seen it's a newer Rev B that you see Mark Morton using.