It is amazing! It's the most noticeable sound upgrade I've made because I have a Nismo Intake and Mossy Exhaust so when the RPM's rise to CVT territory, the car just screams its way to the new 7200 redline. Before the flash, I could feel the car start to bog down around 6200 as it approached redline but now it pulls hard all the way! When you shift into second, it feels lke it wants to rip the tires off because it falls right into the sweet spot on the powerband. Let me just put it this way, whatever lags there were at high RPM's and when upshifting are now gone and it feels like there's at least a 10-15 HP gain from it. For details on the technical specs of the upgrade go here:
http://www.technosquareinc.com/altima.htm
Even though they don't show the SER on their price list, trust me they have it....