Mesa were smart enough to wait and see how the technology developed. They then entered the market when they were sure they had a product that would beat everything else and you'll be hard-pressed to find someone who doesn't appreciate the Subway series as truly top-level products. Maybe not to everyone's tastes, but the quality and functionality cannot be denied.
I owned one class D head before I got my D-800... a Genz Benz Shuttle 6.0, which was awesome and I loved it. Sold it off when I was in a spot of financial difficulty, regretted it later on, but then I got my Mesa and all is right again.
@agedhorse : My suggestions are as follows:
1. Maybe a tube-pre D-800? That would be sweet. Leading from that, the solo funciton on the M-Pulse and Prodigy was useful, maybe something along those lines would be a nice addition. Or maybe a separate drive knob/boost to get the best out of that tube-pre? Footswitchable would be cool but not vital.
2. The voice-knob with the Carbine-style mid-boost as well as mid-scoop would be nice. I usually have my EQ relatively flat, and adjust according to the room/stage, but on some stages I find I definitely need a boost rather than a scoop.
3. A 4x10 cab with the same footprint as the existing Subway cabs would be awesome. I know, I know, I could get 2 2x10s and stack them, but surely the weight saving would make up for it.
I liked the idea of the Prodigy/Strategy amps but the reality is that they're just not practical enough for me now that such light/compact alternatives exist. I don't have a road crew to load in/load out a big heavy cabinet and a big heavy head (by today's standards, 30lb is heavy...) I love my GK setup but I'm seriously thinking of selling it, for that exact reason. My Mesa rig gets almost all the gig time and use, especially for overseas gigs. Even with local gigs, I can fit my entire Subway setup into the back of my Astra without even taking the trunk cover out. It used to be that having a class D rig was a compromise - you're sacrificing something for that light weight and compactness, but that's not the case anymore with what Mesa have produced.