My wife and I ate Bistecca alla Fiorentina in a restaurant famous for the dish. It was fine, nothing special, I've eaten far better steaks elsewhere. We were assured that the beef was from Chianina cattle which is the traditional breed for the dish (I'd eaten some Chianina steak in Rome previously as well) but I was underwhelmed by the taste. I've had consistently far better tasting British beef and also some great grass fed beef (I think it was finished on grain to balance the flavour) in the US (not the intensively reared feedlot beef) so I'm not sure where they hype comes from (although considering how many Italians view their cuisine as the best I can guess).
Also, because of the size, several inches thick Porterhouse it's intended for sharing and it's also served quite rare. I overheard some people complain about the rareness but I don't understand how they think such a thick piece of meat can be cooked to medium on a grill.
As has previously been pointed out, it's a simple dish, a grilled steak which any competent chef should be able to do with their eyes closed. For Bistecca all Fiorentina to be authentic it has to be made with Chianina beef which, in my opinion, is the problem, there's much better beef out there.
So to answer your question I would recommend not getting too overwhelmed by it. They're all going to be similar, it's difficult to get the dish wrong so go on intuition. Besides, Florence isn't known for its food, I've eaten far better food elsewhere in Italy, every meal in Florence was a disappointment so go in with low expectations and if it exceeds them then it's a success!
