For the money that you would spend, they're not worth it. There's no real noticeable gain for as expensive as they are. I would expect that Todd Z or someone who's actually installed and tested them will chime in soon with a similar opinion.
If you want to upgrade the exhaust, you're better off spending your money on a good muffler like a Flowmaster, the Random Technology Y-pipe and high-flow cat. You can get the pipe and cat from our sponsor, Zabteck.com.