There are many, many threads about TREs. Here is but one:
http://forum.svrider.com/showthread.php?t=55272
I have one installed in my '07. Many people will tell you they found 10 extra horsepower when they added a TRE, while others will tell you they noticed nothing.
Personally, I noticed a
very subtle difference with the TRE, in that the throttle response feels a tiny bit more responsive, crisper. But keep in mind that the TRE only works in the first 1/2 throttle: once you twist the throttle past the 1/2 way mark, the timing isn't being retarded anyway so the TRE is not doing anything at this point. If you're looking for more power, just twist your throttle wide open instead.
There is no damage being done to your bike with a TRE. Suzuki purposely retards the timing of your ignition as a way to meet exhaust emissions and noise pollution standards. A TRE simply overrides this, making your engine run the way it should. Just don't expect a big difference. It's barely noticeable, if at all (and you really need to be paying attention before and after).