I have two pc's and a laptop. With all three running Windows 7, homegroup worked perfectly, with all computers able to access the files on the others exactly as one would expect. I installed Windows 8 Pro, which I downloaded recently from the MSDN website, on the laptop. From the info on the MSDN website, I believe the version downloaded is the official release version, not a release candidate. The install preserved all settings, apps, and files.
I cannot connect to the homegroup from the laptop. Well, not exactly. I joined the homegroup during the install, and later left and rejoined, that was advertised as being offered by one of the pc's (not sure why that one was picked and not the other or both). This homegroup appears in my "computer" folder in the file explorer, offering files from that pc. But it excludes documents (only the music, pix, videos, and playlists folders on the one computer appear). I can actually access those files from the laptop.
But the Homegroup folder, which actually shows all the computers by account and computer name and includes documents from both computers, does not open those folders when clicked. The computers listed by name in the Network folder give me a login that doesn't work. It asks for a username and password, no combinations of which work. Further, the following error message appears before the login is even attempted: "The system cannot contact a domain controller to service the authentication request. Please try again later."
The two windows 7 pc's continue to share all files, including documents, seemlessly. I can also get to the laptop shared files, which I shared during setup, from either pc.