Just gor myself a MK1 112 also, with the FBV Express for next to nothing (200$ Can)
Most notable differences:
-No USB, so no way to update firmware or edit patch and upload them on the amp
-Missing 4 amps settings
-More pressents (300 I think, same as Spider III)
-No Quick Loop
Good sounding so far, I have yet to crank it up to hear the lamps, but I feel like they need replacement. For the Pream at least, I can hear when I change channel in the amp!
I'm not sur if I'm going to use it only as a "power amp" with my ToneLab EX, it feels like I have more tone selection on my ToneLab, just not sure of the difference in tone yet.