Well, I actually have one, and have had it about 2 years/3 crx's worth. It's even survived a crash, someone blasted the rear driverside and the seat area was all fine. The rear fender folded, and the interior piece went in a bit, but not far enough to hurt someone. Whats really dangerous is your head location, directly under the hatch glass/ next to the rear quarter window. A good hit would send your head through either easily.
I've ridden in the back seat plenty, and so have several tall/fat people. Lets just say your not riding 4 deep in your car often, if at all (I wont, it's too cramed) I'm 5'10 and my head has about an inch or two of clearance sitting up straight. You can easily and comfortably fit 3 in there.
Over-all I love my rear seat. It looks nice, people jock it, comes in handy, and most importantly it's JDM. I paid around 700 for mine in mint condition shipped from the UK, from
www.s-and-g.com but off an eBay auction.
Definitely worth it, takes 1 hr for a very easy install