Here is the error message I received when I tried to start playing from the new launcher.

---- (We'll do this automatically later ;D) ----
Client> 2013-07-01 14:33:47 [CLIENT] [INFO] Setting user: GUNR23
Client> 2013-07-01 14:33:47 [CLIENT] [INFO] (Session ID is ${auth_session})
Client> Invalid memory access of location 0x0 rip=0x0
Client>
Game ended with bad state (exit code 139)
Deleting /Users/lazarus2391/Library/Application Support/minecraft/versions/1.6.1/1.6.1-natives-1372703625678579000