Its been roughly a week with my gumby/mj2 and I can confidently say that it is a deadly duo. It is a pretty massive improvement on my bifrost uber/WA7 (gen 1) setup I had before, mainly I think that the gumby is just simply better than the bifrost uber is every way. However, I have to say that the WA7 is extremely competent.
The WA7 vs Mjolnir 2 is not exactly a fair comparison but the little woo amp is extremely competent. I have upgraded tubes in it, and stock tubes in the Mjolnir. The WA7 does not have the space nor the air the Mjolnir has, and the Mjolnir does a better job in tightening up the bass. Even so, the WA7 is more musical to my ears, and a better pairing with the th900. Really I think its just obvious I need some new tubes for the Mjolnir. I feel like the stock ones hold it back a lot. In fact I prefer the LISST tubes to the stock ones schiit sales.