I've had mine in for about a week. I can honestly tell you the difference is significant, and immediate. I actually have to pay close attention to throttle position in 2nd gear, or the tires will break loose at around 3k rpm. I've kept it at the default setting of 4.75 psi (i believe it is). Max setting's at 8 psi. The new units look a lot higher quality than the former. The power difference you feel will be in the low to mid range. I've noticed the biggest improvement when downshifting to 4th to pass. The slight lag (for lack of a better term) is gone, now.
Just as important as the noticeable power increase, is the customer service I've gotten from Ameya. They stand by the product 100% and will do whatever it takes to keep their customers happy.