i've put together a comprehensive post about this mod here
the pic below is a GSXR1000 pipe 2003 can on my dr650.
click on the photo below a slideshow showing the flange, stainless steel mid pipe, brackets etc.
impressions? saved a huge amount of weight and it looks much better than the standard pipe. its got the suzuki markings so little chance the cops would hassle you about it. its not much louder than stock but has a beautiful deep note.
definitely is less restrictive, can feel a definite improvement in low and mid range power now - there's a dyno chart showing gsxr versus stock and FMF pipes. only decrease in power is the final 500rpm, but how often are you going to be flat lining your DR? this pipe makes a world of difference in the revs you'll be using 98% of the time.