More acceleration, more agressive throttle reaponse.
Up 600rpm above stock.
Still 175-180+ mph top speed.
Unrestricted gen2 can do 197mph with stock 18/43 sprockets.
Slightly lengthens wheelbase, vs a +3 rear, very close gear ratio, slightly shortens the wheelbase
Only cons would be the above, if that's not what you like, and isn't ideal for someone that just wants to cruise or tour, as well as a small drop in mpg.
Personally, I love it, and do -1 front or +3 rear to All my bikes, so my opinion is biased, but the above are facts.