Proving conclusively that I live in a different universe.

That may well be, but I think your statement was essentially true - valves are normally open (loud), and it takes vacuum to close them.

Has anyone noticed changes in driving characteristics when making the swap? I just installed the V8 exhaust on my V6 and am noticing that when driving and letting off the gas pedal, the car seems to "coast" and revs seems to hang a bit longer than with the V6 exhaust. Does this have something to do with a decrease in back pressure? I find these new characteristics actually much more appealing.

Additionally, I'm also noticing a bit more low end torque.

Is this all in my head?

Yes, but I'm always in sport mode.

Mostly in your head ;) , but the overrun (snap, crackle, pop) does indeed seem to last much longer.

Although, I want to believe that, I just went for a nice drive and I'm convinced the reduction in back pressure has to do with the more free flowing de-rev characteristics. The car does absolutely behave different with the V8 muffler which was set to valve open at all times. I'm 10% sure it's in my head, and 90% sure there is some truth to it. I want to know if anyone else has experienced this though?

If this hasn't been said already this is a 100% easy swap, everything lines right up once you get the V8 valance. The valves are open by default, with them closed the back pressure for sure makes the car accelerate much differently. The exhaust gas velocity and therefor scavenging is increased causing more low end TQ generally....but this back pressure will start to hinder the superchargers ability to move air as RPM increases(superchargers move exponentially more air the higher the RPMs) so a free flowing (but slower velocity) exhaust will provide more total HP.... Anyone doing this swap without active exhaust button should look into a small vacuum pump with a remote to control the valves. i have seen them with the RF remote on a key chain for under $75. would be a super simple to install and an added bonus is you could closed the valves before you start it if you wanted to be quiet.