to each his own. I really like the tail of the 04/05 600/750 and I think that that exhaust takes away from the whole look of the bike. plus more piping = more weight. if that is the look you like then go for it.
Read an article in a mag a while back on that exhaust. The reviewer was totally hating it! In fact, the pic they had of the article had her throwing it in a dumpster! She said it was super heavy, and sounded like crap...
Wasn't there a short editorial piece in SR recently about the evils of undertail exhausts? Like jacking all that weight up high and the added restriction caused by the extra pipe length? maybe having 2 exhausts defeats the restriction issue but what about the weight issue?
Personally I'm a fan of the Buell's bottom end exhaust but I can't say I care for their bikes.