Lufthansa is a fantastic airline with great service. If you read the other threads about best/worst airlines I think you'll fine others who agree.
Business class seats are wider, softer and have more features than
Coach, such as deeper recline angles, footrests, a tray table that folds out from the armrest, a wrapped blanket, amenity kit, and usually a personal TV monitor with a selection of movies and TV shows (this varies from aircraft to aircraft, depending on flight duration). I remember Lufthansa offers on-demand programming on the flights I took, so you can select what you want to watch when you want to watch it (in other words, you don't have to join a movie in the middle of it). It may vary by aircraft, though. But I would expect this to be the case for your long haul from Seattle to Frankfurt.
Depending on the airline, some Business Class seating in 747s are in the upper deck, which I completely prefer. It's quieter and seems to have a smaller number of passengers and 2 flight attendants and 2 restrooms. Downsides are reduced overhead storage for hand carry baggage, but there is a closet at the top of the stairs to stow any hand carry bags that are too large to fit overhead. Ive never had any problems. Also, at the window seats in the upper deck, there are small storage compartments alongside the window for personal items. You can check with the airline or your travel agent to determine if your aircraft is a 747 and if you are seated in the upper deck or downstairs.
Business class service is also a huge notch above Coach, with an improved flight attendent to passenger ratio. Drinks are served pre-flight and you'll receive a menu with the flight's meal and beverage options. Business class meals are typically 3 courses, starting with an appetizer, main course and dessert. Drinks (alcoholic and non-alcoholic) are served throughout and you can also go to the galley to request refills as you need. Sometimes the airline sets up a small table in the galley area with snacks for passengers to enjoy throughout the flight.
Business class passengers also have the opportunity to board earlier than Coach. And at check in, there are usually separate check-in lines for business class passengers (depending on the airport).
While you are waiting for your connection to Florence in the Frankfurt airport, you can visit the Lufthansa Business Class lounge for drinks, food, Internet connection, restrooms (I think showers too), reading materials, etc.
Have a great trip!!