I DON'T have the X-TRE, but I do experience a very very very slight surging at constant cruising speeds and my bike is 100% stock. Like you said Liquidysplit, it doesn't show up on the tach, but I feel it and it really is ever so slight. Now that I think about it, it seems to come and go, I don't think it does it all the time.
I am thinking about getting the X-TRE, but there just seems to be such a negative thought about TRE's that I am still a skeptic. I have yet to see any dyno numbers from anyone to show it really does what it says it will do. I realize the website shows an increase, but would be nice to confirm here in the good ole USA. Anyone?