IT's not just horsepower on paper. The FEEL of a V twin will crap all over the BORRING inline twin of the GS. DO IT!
+ 1. Totally different engine. Personally, I'd be all over the v-twin vs an inline twin.
I disagree somewhat with others in regards to trying different bikes - as long as money isn't a pressing issue, I say try as many different bikes as you want to. No one says you have to be faithful to any particular bike for any specific amount of time.