I received mine today in Canada! I loved the original Vali so I was not sure how much improvement to expect. I was simply blown away! First of all, the hiss is completely gone on both the low and high gain modes. I have the AKG Q701, Fostex T50RPmk3 and Grado SR60e and even the Grados are completely hiss-free. On the original Vali, the SR60e had an audible hiss. However, what truly surprised me was how much more black the background was on the Q701 and T50RPmk3. I guess I had gotten used to a very mild hiss on the original Vali even on less sensitive headphones.
As for the sound itself, I do not speak the audiophile lingo yet, so please bear with me. Keep in mind that I am comparing it to the original Vali only since it's the only other proper amp that I own. I would describe the sound on Vali 2 as much more robust in a good way compared to Vali 1. The original Vali had a degree of lushness that was very enticing but it left its imprint on all the music that you would listen to. Vali 2 is more neutral (at least with the stock tubes), but still has a great full sounding tube sound. It definitely sounds more natural and fuller then the original Vali. It also sounds more stable and competent - maybe it has to do with the fact that it has less distortion.
I have not done any scientific testing, but I feel that Vali 2 has a much more well defined and grounded low end. The drums and bass sound spectacular. It pairs extremely well with the T50RPmk3. The Q701 also sounds great. I will test it later with the Grados.
As for the ringing and microphonics, there are none. Does not matter if you plug in the headphones, or flip the low/high gain switch, nothing.
In conclusion, Vali 2 is a big improvement over the original in both the sound and functionality. It is also a great value even taking into consideration how bad the Canadian dollar is right now.
If anyone has any questions, I will be happy to try and answer them.