Pretty much what everyone's said here. It has a nice howl to it especially at the 5K plus range but it's still fairly subtle compared to the Trident which has a beautiful note but is a few hundred $ more and apparently a little more difficult to install. More importantly, it adds a little hp and opens up the mid-range a bit. It won't bother you on the freeway (nor likely other drivers either.

)
One thing I do notice is that it takes a little while to warm up. When you first fire up cold, it doesn't sound much different than the stock. But once it heats up and expands a little, that growl starts to show up.
Not a bad can for the $$.
p.s. I actually like that 'groan' it has in the 2800 - 3300 range! :-D