http://i.imgur.com/siVEek2.jpg
Blizzard just opened up its new Battle.net client into open beta for anyone to test. I tried it out on my Mac and found the download and install to be a very simple process. The Battle.net client has a slick layout and is fantastic to use. I hope over time they keep the simplicity of it all.

"The new single sign-on functionality allows players to log in once to access World of Warcraft, StarCraft II, Diablo III, and the upcoming PC and Mac versions of Hearthstone: Heroes of Warcraft, and stay logged in for up to 30 days.

Players can also install games directly through the app and, if you choose to leave the app running on your desktop, keep them up-to-date automatically even while you’re away from your computer. Please note that it’s entirely up to you whether you wish to leave the app running—you can exit it at any time, and it will automatically re-launch whenever your standard launchers would.
"

If you want to read more, check out the Blizzard post:

http://us.battle.net//d3/en/blog/10626946#best

If you just want to download the new client for testing:

https://us.battle.net/account/download/index.xml?show=bnetapp