I should start by saying that Florence is quite possibly my favorite city in the world, and this passion for Florence colors my review.
Il Salviatino is a gorgeous Tuscan hotel, and a wonderful experience. But I think it is important to know what you want when you are booking a hotel in or around Florence. If you want a hotel in Tuscany, that is near/convenient to Florence, then Il Salviatino might suit you and is indeed wonderful. It is relatively easy to access Florence by car or shuttle. However, if you want to be in Florence - if you want to wake near the Arno, and really feel the intimacy of Florence (and despite the crowds and tourists, Florence is one of the most beautifully intimate cities in the world) - then I actually wouldn't recommend Il Salviatino.
But let's assume you want to be in Tuscany (not Florence), then Il Salviatino will provide you with a beautiful, elegant space, fine food, and a gorgeous view of Firenze in the distance. The public spaces in the hotel are stunning - high ceilings, tasteful, minimalist, almost manly decor. Uniformly lovely. And in the height of summer, the pool was much appreciated. Having said that, I actually think the time to stay at Il Salviatino might fall or winter, when the gorgeous interior space can be appreciated and fully utilized. The interiors tend toward cool and dark, a stark and slightly jarring contrast to the bright sunshine of an Italian summer.
The staff were very good, and tried quite hard, but still missed a beat or two (restaurant reservation request ignored), toiletries had to be requested rather than just replaced), but these are relatively small matters.
Ultimately, I would recommend Il Salviatino very highly, for a Tuscan, but not necessarily, Florentine experience.