Mine's relocated to the rear and it's very worth it if you're into performance. If you're using it as a daily driver, it's probably not worth it. In mine, it's an Odyssey PC680 mounted in the rear right, giving me a 15lb battery back there instead of a 35lb battery up front. Any weight you can pull to the back of the car will help in the overall balance of the car and that's a big weight.
I mounted mine on the flat to the right of the spare tire well, but did have to cut a little of the interior panel to make enough room there. I'll try and get some pictures this weekend at the next autocross, since I'll have the back emptied out again.
-N