If you are worried, change the oil, check the tire pressure, make sure all the other fluids are full (brakes, clutch), maybe check the chain tension, lube it if it suits you, make sure the light bulbs are all working. Then get on it and ride. Yes, the clutch will make some noise in a few more thousand miles; there are fixes for that. Yes, you'll probably want to add a PowerCommander or Flash the prom, but that can be done. Yes, you'll want to sync the throttle bodies someday and put some fingernail polish on the adjustment screw to better fix it in place.
Then, when you wheelie away from a 650 wheezing in your dust, you can grin and say to yourself, "yep, made the right choice." I've owned both versions and would not EVER go back to a 650. Not even the new one. (Tongue in cheek, of course.)
Steve