I was able to launch snapshot 13w23b fine since it has come out but today with the new updated launcher it won't allow me. Here is the information it provided me in the development console:

---- YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
---- YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
---- YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
---- (We'll do this automatically later ;D) ----
Client> Error: Could not find or load main class Huffman\AppData\Roaming\.minecraft\versions\13w23b\13w23b-natives-169405243860665
Game ended with bad state (exit code 1)
Deleting C:\Users\Michael Huffman\AppData\Roaming\.minecraft\versions\13w23b\13w23b-natives-169405243860665