Yup, sure looks good and sounds great.
For now, I'm not willing to pull the trigger on a $3,500 mod without a brochure, reviews, a web site with product details... something beyond a forum post and a YouTube video that contributes toward my gaining peace of mind in the purchase and an understanding of the credibility of the product and the manufacturer (no offense intended toward you with that comment, of course, I simply don't know anything at this point).
Can you help me out or are you still in early stages?
Here is a link to my review of the exhaust: http://www.m5board.com/vbulletin/f10-m5-discussion/331585-rpi-gtm-resonated-review.html
And video: https://www.youtube.com/watch?v=nmjIm-skUWg&feature=youtu.be
There are reviews and videos of the exhaust by other members as well.
I've had the RPi GTM exhaust on my car for about a year now, swapped out the resonated section for the full straight pipe setup sometime in April this year. It sounds absolutely incredible, and the power gains are noticeable over time. The video is of the exhaust before I removed the resonated section. Also, I have stock cats in place, haven't gone catless.