My ST-70 kit + VTA board I built last winter is running great and now actually seems to be sounding better! Having built it myself I was kind of worried that small issues relating to bad soldering joints etc might surface over time, however the amp is still dead-quiet and perfectly clean-sounding (no humming etc), the Gold Lion KT66 tubes are still running beautifully (I have seen some complaints on the guitar amp forums regarding the reliability of modern Gold Lion KT88 tubes, so I have been a bit suspicious - seems the KT66 variant is fine). I would guess that it has been running in excess of 1000 hours over the past 18 months and it has been a joy to listen to.
I have discovered Triode mode (my kit had the Triode/Pentode switches), I initially did not really notice a difference between the two modes but lately realised that there are subtle difference - I think I actually prefer Triode operation for small Jazz ensembles and Classical music, when I go back into my Progressive and Industrial Rock mood, Pentode operation seems to sound better.
Because of the success I had with this amplifier I am now a Dynaco "Fanboy", I am gearing up to build myself a pair of Mk. III monoblocks. Additionally, I am hoping to build the VTA preamplifier as well (I am still running my ST-70 in a "hybrid" configuration with a solid-state NAD 114 preamp - reason being that the NAD preamp has a VERY good sounding built-in moving coil phono amplifier).
-- JunkyJan in BC, Canada