There was a thread almost identical to this a few days ago. I'll repeat my thoughts, nonetheless:
I think Vai has terrible tone, and I felt my tone was terrible when I bought an Evo and put it in my floating-whammy Ibanez.
I put it in my hardtail Charvel a year later, and was nothing short of stunned at the difference (this was about 8 years ago, when I was an idiot).
I love the pickup now.....it's not too overwound (around 13k?), so there is still "fairly' good definition across the strings when playing chords through heavy gain. It's tight, tight, TIGHT.
The bottom 'E' string is just.....*TIGHT*.
Having it in a hardtail really helps smooth-out the upper midrange, as well. I love the pickup in my "stunt" guitar. It's not in my main axe, of course.