I have scheduled a test ride for this Saturday. I will be able to ride both the C650 and the C600. I am more interested in the C650 but it will be interesting to compare the 2 scooters. I've been reading about the C650 and it seems to be the new benchmark of GT scooters. I'm thinking it should be a good alternative to touring bikes. It's also half the price of a BMW R1200RT (loaded with options).
There's a comparo between the R1200RT and the C650 here:
The article is in French but the rating is at the bottom. Considering how good the R1200RT is, I would say the C650 did pretty well.
There's also a comparo between the Burgman 650, the Aprilia SRV 850, the Honda Silverwing, and the BMW C650GT (also in French) here:
Google will help with the translation.