Playing on servers different than one's own will be made available through a patch "in the coming months".
It will no longer be necessary to purchase different clients to play on different regions: like it is in Diablo 3, SC2's global play will allow seamless switch between servers from the log-in screen and will feature the characteristics described below:
Each region will have separate profile, i.e. ladder rankings, progress, friends lists, etc,. will no carry over when switching servers
When region's server is under maintenance, players will be able to switch and play on another
Game language and interface options will remain the same when changing servers
In-game policies of the selected server apply
In typical Blizzard fashion there is no set date for when Global Play will be available but as no Heart of the Swarm is mentioned it looks like StarCraft 2 fans are likely to get it before the expansion launches.
Source: Battle.net
