Spent some time with it tonight (a rehearsal was cancelled due to weather), and made sure to pull out the Y cable and the Pedal Power II+ to see what I could find out with different voltages.
Like the previous incarnation, I found that when you up the voltage, you lose a lot of the syrupy sound that the filter has. When it was at 18v, it was almost as if the pedal wasn't on for a couple of lines I was playing; it just popped in and out for a couple of parts. When I put it back to 9v on the same knob/switch settings, this filter was THERE. And it was there in spades.
However, one thing I noticed is that on really fast stuff, it was easy for me to get ahead of the filter. When you bumped the voltage, that filter really followed you. 16th note lines that in 9v seemed a little muddy on certain settings really jumped out and grabbed you with 18v.
I also noticed that the overall tone of the filter gets more aggressive as the voltage is upped. At 18v on a couple of settings, it had that slightly overdriven filter thing going for it; the same settings at 9v yielded a thicker, more synthy tone.
Overall, for me it's going to depend. While the previous version I was completely sold on keeping the 9v on it at all times, I can definitely see where I might rather have some extra voltage on it. Using the SAG outlets on the PP+, I could drop the voltage at different intervals to see where that sweet spot of keeping that syrupy filter but with the speed and bite would be. I think it's around 12v-15v (give or take), which I think is where I'm going to keep this one.