OP, if you're coming from a 200kg bike, the bike is going to feel a bit heavy at first, and depending on the 650cc, it may feel a bit slow, both in acceleration and stopping. Fortunately, the weight is carried fairly low, and the bike is very easy to acclimate to.
For reference, I'm a newish second hand completely stock ST1100 owner, 1999 with 47K miles, about 2K of which are mine, mostly short commutes in a suburban town, a little highway miles, and a spirited canyon ride or three
. I paid $1500 USD. My other rides are all performance and performance-ish bikes spanning almost 40 years, most of which weigh 200kg or less. There is no getting around the ST1100's 320kg curb weight -- it steers heavily, stops slowly, and accelerates linearly/smoothly but "unexcitingly." That said, it's been an unexpectedly fun ride for me so far with little drama except dragging some hard parts a couple of times, but I'll be the first to admit I ride somewhat spiritedly. Almost no mechanical or electrical issue so far.
I recently rode a MT-07, 200kg (with backpack) 689cc, halfway across the country (about 1500 miles) to deliver it to my son in the Army through a 55-degree F temperature delta and fair, windy, and rainy weather... it was NOT fun or easy. On the ST1100, it would have been fun, comfortable, and very easy. HTH, and best of luck!
