We've had a lot of fun on a 1995 or so Santana Visa.
We were thinking of a Cannondale RT2 as a modern upgrade.
We tried one. Yes, lighter, faster, peppier and the gears and brake improvement were a whole generation better
We tried that one in UK on our last leave there in August 09. I was just about to ask the shop to send it to us - but then I went and hurt my leg.
Now I'm about ready to tandem again, and spouse is about ready to trust me again!
But, here's the thing -
The shop (Northern UK) that let us try the cannondale and to whom I'd like to give the purchase, has an ex-demo Santana Beyond with S&S couplers. Not new, but as good as.
It's 3x the cannondale price, and I know there's a diminishing return on bike expenditure and we probably can't use the Cannondale to its full extent