hiya! I don't have the Siena... but the Tuscany... I was originally on a Lemond Buenos Aires... and had the same experience as you are describing when I first rode the Tuscany... 2 laps around a parking lot and there was zero doubt that THIS was my new bike!

It climbs great and descends like a dream... very stable, light and fast. I've had it a couple years now and have never once had an urge to even look at a new road bike... I could not be happier with it. I have ridden 5 centuries on it this year so far... just a comfortable, solid ride.