Out of the box, I felt the pickups were poorly balanced compared to my 4 string P's. As mentioned, highs were harsh and the lows lacked definition. I thought something was wrong with my pickups, but I guess it's normal. New pickups still sound raunchy running trough ampeg svt350 with 8x10. I love it. I don't think you will be disappointed with the swap.
elBandito, how did you evaluate the original PUP? Did you gig through it, record, etc. I only ask because I have full American P5 electronics but have not installed as I'm pretty happy with the stock VMP5 tone. If there is a compelling reason to change them out I will, otherwise I'll just hold onto the P5 stuff until something fails.