I have it and it is really weird having it there. Not only does it not sound very good (not horrible either, but not great.....) but it gives your right leg a buzzing feeling having it right next to it when the bass hits.
I thought about getting something like the aftermarket ones available for the rear from quadratec too....but at the end of the day, I didn't want to give up the room in the back that I use for storing stuff just to have a sub that I might have trouble hearing in the first place if it is placed that far back. Don't know if that's true, but I don't regret having it set up the way I have it now.
Also, I wasn't sure how it would work with my aftermarket radio and speakers, but it was installed seamlessly and seems to not have any problems.