I just downloaded the latest version of the beta as of this morning (2/22/16) and it hangs on start screen.
This particular installation had been updated a few times so I went ahead and forced the program to stop using Task Manager. I then uninstalled MP and went on to the C: and deleted the MP from Program Files. After this was done I went out and downloaded the latest stable version, ran it to verify that it was working and then updated to the latest beta again. Same result.
Not mission critical that I use the latest beta so I'm fine with reverting back to the stable version. Just passing along information in case Michael O. is watching or to see if others have the same issue.
Hardware is Surface Pro 3 128 GB, latest OS patches etc.