I have an 07 SS with the stock exhaust (I have a Jardine on order) and honestly, its great! You have to remember that most of those reviews come from one of two places 1. a professional rider (who can feel ANYTHING "wonky" on a bike and have very strong opinions based on TONS of EXPERIENCE) and 2. average guys like me with OPINIONS based soley on OPNION and tests they have read, therefore when they put on a performance mod what they read is very easily felt (a mind thing if you ask me). In a nutshell, all those tests and stuff are out there to make us lust after more and "better" parts...marketing in other words!
I am not saying that these parts don't create more power and CAN be noticable, but I am saying that no matter what ppl say about the stock exhaust...the bike is friggin' loads of fun to matter what pipe you put on it!
My suggestion is to keep the Jardine exhaust on untill it blows its load, then at that point, stick the stock exhaust back on and let me know how wrong I was about this rant!
LOL
Hope this helps!