Now, it's compatible with Vista and Seven. We don't know for XP.
Custom Map Patcher is a tool that allows you to play custom map on Battle.net. (EACH PLAYERS MUST DO THAT) Do this process for all the friends you want to play with:
- Create the map "Lost Temple" on Battle.net and everyone join it
- Launch the map patcher
- Select the map you want to play and click "Patch"
- Go back to SC2 and start the game
Battle.net map upload is going to be released before the end of the Beta within a few weeks. This technique is a temporary workaround that should let you start doing multiplayer maps right away!
SC2 Custom Map Patcher 2.1
SC2 Custom map patcher 2.0