Matt's had one in stock and it followed me home.
Haven't had too much time with it yet, and I'm on my way out the door, but my first impressions are:
1. Lots of controls (as usual with the Mark series) - its going to take a minute to understand how they interact.
2. The 5-band EQ is amazing.
3. The crunch mode on channel 1 that sounds so good in the Petrucci demo video is indeed awesome, but the Mark IIC+ and Mark IV modes on channel 2 might be even better.
4. I'd forgotten how awesome tube amps feel.
5. Probably going to need a boost to smooth out a rhythm sound on channel 2 for leads.
Shitty low-light cellphone pic and no recordings for now: