I put the Pro-Series Hypercharger on my 2005 Vulcan Classic at the same time that I added DG Hard-Krome 3" Big Straights and a Cobra Fi2000 fuel processor. The performance difference from stock is impressive, especially at the top-end. I love the sound when I get into the throttle! The Hypercharger and Hard-Krome pipes pair very well with Vulcan 1500 engine; the sound is very sweet (and deep). I cannot say if the Hypercharger alone will give as good of results, but I definitely agree with fobears that it is difficult to quit smiling when you are riding with the Hypercharger set-up.
Also, the Hypercharger does get in the way of your knee, but after riding my bike with it, there was no way that I was going to remove it. I moved the right floorboard out about 1.5 inches and added a longer brake pedal.