went across a complete lane just over a week ago on a 990i, they are a bit slab sided, and it was a VERY WINDY DAY. May be better it i ate more pies. Dont let it put you off! it`s still a great bike.
Not as stable as an 1150GS, no. However, I did find that tweaking the suspension to the 'Sport' settings from the owners manual helped by giving more feedback on what the front end was doing. As well as generally better for road riding in the dry, this has made riding in wet and windy conditions a little less
I don't find mine worryingly wobbly, but I never do 110 mph either
A smaller front wheel might well make the bike a bit more "positive", if you are only using it on the road. They are "slab sided" though as Nick says and will always catch sidewinds to some extent.
Seconded - alternatively could try a fully laden Pan European if you want to be completely impervious to cross wind
Seriously though, if you are really concerned and I can't say I've noticed a problem in my relatively short period of ownership, there are a few threads on Orange Crush where people who have had problems have cut a few inches off their screens to good effect