What Frank said about tube rolling has been my experience with the Ultimate 70. I've decided that I liked this or that brand, but then when I've switched back to something I had in earlier it has sounded just as great. JJs, EHs, it's all good. Strong reliable tubes are the ticket, not NOS. His circuit doesn't seem to really care which brand of power tube it is.
The lack of an IEC would be a very, very silly reason not to try this amp. Just compare it to other amps using aftermarket PCs and see if you like how it sounds better, instead of worrying about how much better it "could" sound if only.
My prejudicial feeling is that someone who can't be happy with this amp (assuming the right speakers) can't be happy. It's a wonderful, gutsy, musical amp that does everything well. The fact that it's done with tubes almost seems beside the point. To me it's not a great tube amp, it's just a great amp.
(And I haven't actually heard the new Ultravalve, but I'll climb on the limb that says it's not a step backward...)