Blizzard is currently testing out a new client that will be similar to the Steam client. The new desktop client has been tested internally and it appears that the testing phase is almost finished, because the Desktop App FAQ was added under the Support webpage.
Only for Windows, OS X users will have to wait. Blizzard is still seeking a developer for the Mac Client.
The Desktop app will replace launchers for all Blizzard games (Diablo, Starcraft, WoW) and work similar to the current launchers, having features such as background updates, repair tools, streaming downloads and much more.
You will be able to chat with all your friends across Battle.net regardless of games they play. You will be able to access the Blizzard Store from the client, news of all Blizzard games are displayed.
Install and Launcher
News - World of Warcraft
News - Diablo III
The Launcher - World of Warcraft
The Launcher - Starcraft II
The Launcher - Diablo III
Settings Tab #1
Settings Tab #2
Default User Avatars
Backgrounds - there are many to choose from, I'm just gonna post one per game // World of Warcraft
Looks promising so far, what do you think?