Read the reviews under the Hilton board for the Hilton Garden Inn. It is a very easy bus ride to the train station or Duomo area. The hotel is like an American Hilton. I did a 7 night stay there last year and did side trips to Lucca, Ravenna and Bologna.
I can also recommend the Hotel Davazanti. It is located right off a street in the heart of the historic centre. I personally prefer this location over the Hilton Garden Inn but I saved a ton of money at the HGI last year.
Thanks for your reply. I've been looking at both actually but as of now both are fully booked. At the moment I'm looking at the Star Tuscany & UNA Hotel Vittoria both of which require a short bus ride to the center. I have to remark though that since they all require a shuttle / bus ride I may as well use points at the Sheraton...