reoccurring issues people are having which i can think of off the top of my head:
bike turns off on down shift
vibration at 5.5k revs
what kind of mileage will you be doing at what roads will you mostly ride on as this will effect reliability.
The infamous 5.5k rattle is nothing to be concerned about. It's a single cylinder engine, It's going to rattle some.
I haven't experienced the bike turning of during down shifts, so can't comment on that.
Personally, I have no issues with my bike. Still very happy with it.
You should have them do the 600mile service as part of the deal.
psssst...... One issue we are not supposed to talk about is how some ceebees can't go on the highway. I mean how can you go on the highway where the posted speed limit is 120km/h with a bike that can do more than 160km/h.

Take the ceebee, you'll be happy with it.