In my experience it sounds completely different and makes me love the bike considerably more!
It emits a lower and deeper note throughout the rpm range.
With the stock exhaust I only heard engine noise - with the oe termi shotgun style I can hear the air moving through the exhaust at all times. When I first reviewed videos online comparing the two (and took my own using my phone) it was very hard to tell the difference - maybe our cell phone microphoness are not good in the low frequencies because in real life the difference I hear is night and day.
The fact that I can now hear the exhaust makes this a more responsive bike to me. I am now less likely to slip the clutch as I can better hear the engine revving and can let it out sooner. It also burbles on overrun / decel which I don't recall the stock exhaust doing. Seems slightly quicker to me, but I could be wrong.
I just got done fitting a second hand Evo-line Termignoni exhaust. As cdadv123 said, it definitely sounds different. Louder by a small amount, deeper sound. The biggest difference is lots more popping and grumbling on decel.