I think the GSAP is great and worth every penny.
It does take time to learn how to use it effectively & smoothly. And if it does mess up it can cause some VERY unpleasant reactions.
For example - coming out of a technical 2nd gear corner, rapidly applying throttle (and i do mean quickly) and snicking into third at high revs. If the asphalt is anything less than perfect with lots of grip, i WOULD NOT use the GSAP. The bike will lurch and be totally confused as the TC light flashes AND the GSAP tries to command a gear change.
Absolutely nothing dangerous happens - but its all a bit embarassing
However, i found that under almost any other circumstances the system works a treat. Sweet, easy and seemless shifts (both up and down all the way to 1st). Even wet, slimy roads; as long as the revs are sensible the GSAP will react perfectly.
Quickfire shifts between traffic are amazing (mostly 2nd to 3rd gear)
I find 1st to 2nd best when TC is off. Smooth shifts are possible, but its a very narrow window of opportunity at the lower-to-mid rev range to get a smooth shift while still winding open the throttle. A clutch-shift is probably quicker most of the time in that case (unless you nail it

)
The latest software update has really made a massive difference to the GSAP AND engine smoothness.
Mine was updated last week.