wrxmax, no burbling or backfiring, I would think that impossible with stock mufflers, so that was definitely not a concern under any condition.
So here's my impression now that I've had a week to drive around in traffic and do some freeway driving:
For $65, I'm glad I did it. I've got a little more exhaust presence without having to do much, or spend much. Now, just to kind of recap here, idle to 2000rpm sounds great, just a bit bassier than stock, and a smidge louder. 2000 to 2500/2800rpm sounds a bit nasal and a little raspy, kind of like a G35. This is the one range I'm not thrilled with, and I'm sure would sound much more refined with an actual exhaust system or muffler swap. Above 2500/2800 rpm, it sounds great, basically the same tone as stock, just a tad louder.
Overall, I'm glad I did it, but the sound may not be exactly to everyone's liking, it certainly wasn't what I was expecting (the change in tone that is, the volume bump was exactly what I was expecting). Not sure if I would recommend this to someone or not, it feels like whether the sound is pleasing or not would be highly subjective, some may love it, some may not, but for $65, I didn't mind taking the risk. In parking garages it sounds beautiful under 2000rpm (not that I'm ever much above that rpm in a parking garage).
Compared to stock it isn't that much louder, but the change is certainly noticeable. Freeway cruising sounds like stock until you're accelerating, then the slight bump in volume is noticeable. It's nowhere close to a volume that would ever bother me, and when I picked my dad up from surgery yesterday, he made no mention of it.