Hi Muz,
620 sport is a fine, fine bike, and a huge improvement on the 600. The enging appears to be very realiable (it's not exactly over-powered!), and the handling is the same stable but manouverable style that the SSs have always had. I bought a solver on in good nick for £3k about two months ago. Now in less good nick but will be returned to its former glory!
Good luck, and ask away if you have any specific questions.
Ali