I can definitely hear the difference. The resolution is the best I have ever heard, and I was super happy with the amp's performance in this regard beforehand. The level of detail is downright scary sometimes.
I'm not convinced it's a sound everybody will love, but some people certainly will. I have a gut feeling that those guys who don't like to use the 3DG4 in their OTLs are going to have mixed feelings about what the HEXFRED does to the sound of an amp. The analogy is rough, but fair enough I think. Romantic is the last word that comes to mind when I listen to this setup. It absolutely does sound good, but it's not the traditional kind of "good" that people expect from a tube amp.