I have had mine for 3.5 years and probably about 40K miles. The power surprised me, but not in a good way. I expected it to be unbelievably powerful whenever I hit the gas, but no. You do get power throughout the powerband, but the really noticeable power doesn't hit until about 3500 rpms. How often are you above 3500rpms? Also, realize that you don't get the real power unless you go WOT. At partial throttle you are restricting the boost considerably so the actual "grunt" is not as I had expected. I guess I expected cam type gains and not centrifugal blower type gains.
On a positive note, when you do go WOT at 3500+rpms the power is phenomenal! The blower is pretty much problem free. Because it shares the oil with the engine when the car gets an oil change, so does the blower. Changing the belt is a serious PITA, but I have only changed my belt once.