haven't tried it, but logically it would make sense that you would get a small (1-2hp) power gain and a louder sound. that said though, the factory exhaust is 2.25" and has a fairly restrictive flow compared to aftermarket 2.5" piping and better flowing (and sounding) resonators/mufflers.
unless you can do all the work yourself (cutting, fab work, welding) to put in a straight pipe, you're going to get the best bang for the buck with an aftermarket bolt on system. having a shop fab and weld in a straight pipe could easily run $200 or more for something with small results and a potential sound you may not like.
just my .02, but stick it out for the stealth.
2010 Volvo C70
2011 Harley FLHTK
Midwest Crew #22