The Game Output window will, after a short period of time, go blank, no buttons or anything. Minecraft, however, works just fine.
Also a minor bug...after an update to/installation of the launcher, it says that it was unable to get some file. I found a workaround, though. I just hit play again, and after a few other errors about not being able to get some different file, it successfully launches Minecraft. I think it's incorrectly assuming that it was unable to get the file, when really, it was too impatient
Can confirm.