AAC/H.264/MPEG-2 support will not be provided to Windows 7 Home Basic and Starter customers. That functionality will only go out to Home Premium, Professional, and Enterprise/Ultimate users. But it looks like there will be add-ons made available (free or paid, it's not clear) to users of low-end Windows 7 versions.

Maximum RAM. All 32-bit versions of Windows 7 "support" 4 GB of RAM, of course. But if you go 64-bit, you can add up to 8 GB in Home Basic and Starter, 16 GB in Home Premium, and 192 GB in Professional, Enterprise, and Ultimate.

Windows Media Player Remote Media Experience (RME) is not available in Windows 7 Home Basic or Starter. However, all versions can share media over a home network.

All Windows 7 SKUs support 20 simultaneous SMB connections. This works out to 10 users, apparently.

XP Mode (formerly Virtual PC). As we first revealed yesterday, only Windows 7 Professional, Enterprise, and Ultimate are licensed to install XP Mode.