I also have a '00 RC51, plus an '06 SM610 and a Highland 950 Motard. The 51 and 610 are keepers. The Highland would be my favorite if I could get the injection right, which I have been unable to do, so it's for sale.
About the KTM, I had an LC4 and it vibrated so much it was no fun, as did my friends LC4. I've heard the new 690 is smoother. Anyway, the vibration of the 610 is tolerable enough that I took it on a long trip, whereas 30 minutes on the KTM was enough.