Mine already came in - sheesh! Props to Massdrop for getting these out quick.
Initial impressions with no burn-in are positive. I've got no noise on either channel - everything sounds great!
5-day edit: Pulled the tubes to take a closer look at them and clean up some dust/fingerprints, only to realize that my amp came with GE JAN-5654W driver tubes instead of the listed GE 5654 ones - NICE! Now this is my first tube amp so I'm hardly an expert, but from what I've read the JAN-5654W's are a considerable step up over the regular 5654's. Maybe that's why I didn't experience any of the popping or hiss that some folks have complained about?
Anywho, I've already got some tubes coming in to do a bit of rolling: Voshkod 6ZH1P-EV and Hytron JHY-6AK5 driver tubes, as well as Novosibirsk 6H6P-I power tubes. The Hytron's actually came in today, and the initial impressions are very positive: the JAN-5654W's sounded a little bit incoherent and muddy in the bass department, but these Hytron's seem much tighter there. They also seem to be crisper and clearer overall. It'll be interesting to see how they sound after a little bit of burn-in, ditto with the GE's.
So far, I'm loving this amp!