BRU Sheraton is a "standard" airport Sheraton, which is to say nice rooms, well soundproofed. The one unusual feature that I recall is that the room furnishings were kind of modernistic for a Sheraton (Danish-inspired?). There are a couple of restuarants, including a pub-style one in the front of the lobby that serves pretty good chow for a hotel.
An airport shuttle isn't needed, just a luggage cart. Exit the lobby, cross the street, and you're in the terminal. Works great unless it's raining.
On my last stay (16-18 September 2001) I was not upgraded as a Gold. Those were unusual times though, and I was happy to just have a room where I could look out the window and see planes leaving for home. YMMV on this trip. Don't recall if there was a Club floor.
The airport has a train station on the lower level, and trains run to the city center about every 30 minutes. Once there, you can take the Metro anywhere. Bruxelles-Midi (Brussel-Zuid) is the nicest station to transfer at, IMO. You can also take a taxi, which will be quicker but cost more.