Well, got the exhaust. Review from my journal on FT86Club.com:
I was up in Toledo today to get the Accelerated Performance cat-back exhaust for the BRZ. It's a nice shop with a good crew. Their development BRZ was parked out front, and I think our two BRZs were the only cars there that didn't have 4-digit hp numbers. Supras galore!
So I drove up there to save myself some shipping and Don offered to hang the exhaust for me. It went on pretty smoothly and looks great. There are pictures in AP's exhaust thread, my car looks much the same just black. The tips fill out the bumper cutouts well and make me wish I had the underspoiler to frame them.
Power wise, there's no real appreciable increase on the butt-dyno. But I wasn't expecting anything from an axle-back. There are two greater restrictions in the exhaust well ahead of it, so the cat-back is not where power will be made.
On that note, I got to drive the development BRZ briefly. It had the stock exhaust back on, but it was fitted with AP's intake. It was surprisingly loud. But at the top end, there was noticeably more power.
As for sound, it sounds great. Good volume without being obnoxious, and it sounds pretty good. Personally, I've never been a huge fan of equal-length header N/A 4 cylinders. And I've had turbo Subarus for years now, which are difficult for a 4cyl to top. But as N/A 4s go, this one sounds good.
There is no highway drone. Only if you drive with the rear seat down or removed will you hear the very slightest resonance that I can't be sure isn't just the tires. So no worries about drone.
When romping on it, the exhaust drowns out the intake sound tube. I may remove it in order to neaten up the engine bay. But sound-wise it seems to be a non-issue with this exhaust.
I put together a video to try and convey the sounds. I tossed it together with a couple free programs, so it's not the best, but hopefully it'll convey the exhaust notes.
Overall I'm happy with the exhaust; looks good, sounds good. I'd definitely recommend it.