I added a 650 to the garage last spring.
Rode it to Road America for the AMA races (about 400miles each way). I replaced the seat with the taller 1000 seat (I'm 6'1"), added Givi lugage, a taller screen, engine guards, skid plate, 16 tooth CS sproket(+1), and center stand. Perfect. Very comfortable, plenty of power for 80-90 on the interstate and 40-50mpg. We have lots of gravel back roads in the mid-west and the 650 handles them much better than my FZ1 but not as well as my DRZ400 (right in the middle which is what I was looking for).
I started looking at a KLR650 (50/50) then pregressed to the F650GS (70/30) then finally settled on the DL650 (90/10).