I just tried the improved pitch block virtual capo. I agree that the latency is very high for the chords setting with the tracking set high, and of course the quality diminishes as the tracking is decreased. The big test for me is to play clean arpeggios at a constant rhythm to see if I'm thrown off by the latency. In its current state I will continue to avoid the chord setting myself. I tried playing with the tracking at zero, and still it was throwing me off.
I tested the notes mode too, where I always set the tracking to zero anyway. The big test for me there is to play a note anywhere from the 9th fret of the G string to around the 17th fret of the high E, to sustain the note and apply wild vibrato. Ideally the shifted tone will track with the vibrato I'm applying with my fretting hand. It was mostly fine, with a tiny bit of glitch on the G, and that was not consistent. I also use a lot of momentary engagement of the notes mode using momentary CS switches on the FC12, and there it felt like maybe it was a little off. Normally I don't perceive any latency at all with pitch tracking set to Fast, as Notes was previously labelled, and Tracking at zero, and I get no glitchiness at all.
Important note: for all downtuning with the virutal capo or harmonizers, I increase the output level of the pitch block for every bit that I shift down in pitch. I have gone up to 12dB in level for an octave down pitch shift. I also apply aggressive low and high cuts using those parameters in the pitch block, going back and forth palm muting with no pitch shift, then playing a shifted tone at the same produced pitch until it sounds completely natural. I do this for the context of the song, so a 4th down in a high register needs totally different settings than on the low E string.
To illustrate: for a 4th down shift played on the wound strings, I'll pick a note central to the part I'm playing, say the 7th fret of the A string. I'll set a momentary CS to engage the pitch block only when I'm stepping on the footswitch. I'll play the 2nd fret of the A string palm muted with no shift, then I'll play the same rhythm on the 7th fret of the A string with the pitch block engaged. I'll increase the level of the pitch block until the pick attack sounds similar between the two, then I'll adjust the low and high cuts, go back to adjusting the level, then the cuts again, back and forth until the low end, midrange, and pick attack are completely indistinguishable. I'll also apply detune to get the pitch exactly the same too, because often you'll hear it a few cents off from what just sounds right. This detuning is extremely important for consonant harmonies. You can really hear a sweetness when you adjust a harmony with detune to vibrate in perfect harmony. That's best done by ear.