I sold my S1000r sport to buy a GS.
Apparently on back roads I am quicker....anyway, bar for 120mph plus lunacy or trackdays you wont be disappointed. Handling superb (though I am looking at improving). 125bhp may sound well down, but the torque/push out of corners is impressive. The electronic suspension works very well. was never convinced of it on the S1. The ESA settings really make a difference. The brakes are not 1 finger strong like the S1, but again its a heavy bike and not designed to be as sharp.
The only negatives I can come up with is ltd tyre choice and the bike is heavy when at stand still. gearbox could be sweeter, quick riding may be ok and doesnt show it up, but riding steady exposes an agricultural change at times.
Pilot road 4s work very well at all speeds, wet or dry. Rear doesnt last long, front will last 2 rears. Though my front is cupping a bit on the sides (Scotland!!). That said, the Superduke that was with us had well ripped tyres (Sportsmarts) and he could only keep up on straights.
150 miles to a tank when quick riding with Fz1s, Superdukes, Zx10 and Hypermotards is a nice plus.