No idea, I find mine as comfortable as a GS, as easy to ride slowly and potter about, but more exciting when you want / need it to be, the engine beats the 1200 GS from tick-over upwards and annihilates it through the mid range and top end.
The GS is slightly smoother, is more comfy for a pillion, has a shaft drive and longer warranty so I can see some advantages, but for a solo rider who is happy to oil a change occasionally I cannot see why they would sell them so quickly?
I still have my 1190 and find the 1290 is smoother and more civilised and better two up (a lot less dive / squat - not as little as telelever, but a lot less than the 1190) it also has cruise control (by far the best improvement IMO) and the TFT screen is nice - I am not a fan of Semi-Active Suspension and Keyless ignitions as IMO they offer little advantage for a lot of extra cost, complexity and more expensive shit to go wrong.
If you liked the 1190 you should like the 1290 at least as much, probably more.