it looks nice, and makes the throttle a bit snappier, and the storage thingy on the other side is great.
but i found it far too loud. the sound booms rather than barks, and got on my nerves.
didn't seem to make much difference to performance either.
don't forget that you'll have to pay the postage from the US plus duty and VAT so it gets quite pricey for a slip on can.
I'd be tempted to go to an custom exhaust manufacturer and see what they could do.
I'm sure someone posted some pictures of a gs1150 on this site a while ago, with a zorstec underseat exhaust which looked fantastic.