Aftermarket slip on? Skip it. For $400 or thereabouts, you can have a nice long weekend road trip and stay under the popo-dar. I like stealth.
I've had them on used bikes, but I never bought them. One (the KLR) was obscenely obnoxious, killed the power and quickly got removed for a nice used stock replacement. The POS aftermarket got tossed in the recycling bin. OTOH, the Yoshs on the Trophy were not obnoxious and didn't offend my sensibilities or hearing. Same with the Remus system on the 1150GS.
I find myself in this camp... My last long term bike had a wonderful Muzzy Titanium and Carbon exhaust that sounded great, but still droned on the highway. As well, the 5-0 did hear me coming enough that I feel it decreased my luck.
Other side of the fence, I liked the sound for 'expressions' sake. Nothing like a deep-throated rumble to get the malingerers in the crosswalk moving, or to make the cutie in the next car smile. (OK, so I'm still 13, what of it?).
BUT... the ZRX has a big boat anchor of a system. Double walled restrictive steel from the headers to the canister, and a stainless canister that is bigger than a gatling water jacket. It's legit huge. But quiet. Oh so quiet. I can't say I haven't been pulled over on it, but I've never heard the phrase "I heard you coming". And I (frankly) have been eyeballed doing Way-F'n-Extralegal
tm on numerous occasions and just got no notice for it because it doesn't shriek and I sit up straight not hiding under the paint. HiViz helps too. I can't hide that I'm there, but not yelling sure seems to screw up their impressions of speed.
That said... yes, I want one. But I dont' want to rejet either. so there we go... Can't have it both ways I guess.
LT