PoorSSJ,
I use the GT's and will never use anything else, and here's why.
I love riding twisties at a very spirited pace, on my 07, but I was never really satisfied with the stock suspension or the turn in rate of the bike. Racetech springs, valves, and spacers took care of the nose dive under hard braking into corners. Ohlins took care of wallow coming out of the corners, under hard acceleration. But the turn in rate was always a bit sluggish. The bike seemed to take a lot of effort to turn into a corner at high speed. I attributed this to the bikes excessive weight, and just got used to it.
About a year ago I put a set of 4GT's on, and WOW!!! Problem solved. The stiffer sidewalls improve the handling immensely, both at high and low speeds.
The down side is that the stiffer sidewalls transfer every bump up thru the tires and into the bike itself. You can run over a dime and tell weather it is heads or tales.
If you ride a lot of twisty roads at high speed you will love the GT's. If you ride a lot of slab, I would not recommend them.
Just my humble opinion.