The eternal battle between solid state and tube amplifiers boils down to the odd fact that by any quantifiable standard, solid state is vastly superior, but tubes just "sound better". Maybe because all the distortion in tubes is odd harmonic (the good kind), instead of the even harmonics of transistors.

That is what makes this amplifier design so interesting -- the design uses modern design techniques, normally used with transistors, and made a tube amp instead. Seems like an interesting idea to me.