Common question, I think - and I'll answer as much as I can
I owned a 2k1 Falco for a while - same motor as the RSV. A twin is a completely different animal in comparison to the inlines you are used to. Where you normally are waiting for the HP/torque hit further up in the revs, a twin hits you immediately on twist of the throttle. Newer liter inlines are pushing some real impressive torque numbers, but a twin just blasts it out on you immediately.
How will this affect the ride? Well, it'll do a few things - first, it will require a different level of throttle control - with all the torque and power coming in so early, where you might be generous on the throttle on a smaller inline, a twin will spin the rear tire much easier because the power is right on. Engine braking is much different as well, as the twin will engine brake with a much higher level and will change the way in which you brake into corners. If you are not well versed in blipping downshifts (although I am sure you are), you will need to on a twin - otherwise, you will be welcomed into the fun that is the locked-up-rear-wheel-on-missed-blip experience (not that I have ever missed one or would know about that kind of thing :wink: ). Most people who move to a twin love it, as the entire experience of riding changes a bit - with all the power right there, it always feels like you are sitting on a missle, even if you are barely moving

The nice part, is that you will get most of what you want on the street in 2nd and 3rd gear. If wheelies are your thing, power wheelies with a simple crank of the throttle will come in 1st and second without trying (with the stock shorter gearing the falco, along with the renegade airbox kit and pipes, first gear was absolutely rediculous in its launch ability). The throttle response is often a bit twitchy on the bigger twins as well, but no more than a duc (or an s3, as I am learning

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The Aprilia motor is bulletproof - very reliable, very powerful, and the 60 degree twin is not very vibey. Slipper clutch helps with the downshifting fun as well. Not sure what the situation with Aprilia and parts now, but a couple of years ago, if you ever needed any parts, you could be conceivably waiting a bit (I had a warrantied seat cowl that took a year to be delivered). All in all, you will be very happy with the Aprilia product.
A good friend of mine has an RC - absolutely loves it - same type of delivery as the aprilia, and its a honda - so you know it'll last forever. Sit on both of them, as the seating positions are a little different, and you'll immediately know which one fits you better.
It's a different animal - I know some who went the twin route and immedately missed the breathing room in power curve of an inline, and the fact that you could be a little lazier with it and corner with less concern for spinning the rear. Most I know who have gone the twin route would never look back. More than likely, coming off a triple, you will like the power response of a twin. I say go for it!
[ This message was edited by: crudmop on 2005-06-01 22:49 ]