Win 8.1 RTM + GA Rollup A clean install
A note for Win8 owners contemplating a clean install of 8.1: Both RTM and GA Rollup A are available from the usual places. If your box has OEM Win8, you can't use the OEM key to install, but must use the generic install key (Google for it). Not sure about upgrade keys.
Win8 OEM boxes have the product key embedded in the BIOS. BEFORE nuking your existing Win8 setup, use Magic Jelly Bean Keyfinder (or similar) to find your product key, and write it down. Once 8.1 is installed, then manually activate it with your old product key, since auto-activation doesn't work for Win8 OEM (at least it didn't for me). GA Rollup A is a combo of 3 patches, and will bring RTM to GA level.
The designation "Rollup A" implies that there'll be more patch bundles down the line. But rollup A will be the only one pre-installed at launch, and succeeding ones will be as downloads.