Yeah, it's the public beta. I haven't had any crashes and my apps all work fine. So far the only thing I've run into with Sierra is my VPN (Express VPN) stays connected but every 5 seconds or so throws an error and for some reason I can't log into my Yahoo account on Safari. Siri on the MB appears to be useless though. I tried "open a new Word document" and it just gave me a list of word/text files on my computer.