I installed Windows 8.1; I can definitely tell its in early beta though. I originally got it for the unified search and greater start screen customization options, but they definitely weren't working correctly for me. The search was really slow and didn't search everything like it was supposed to. It looked like it was only correctly searching everything when I clicked into it's specially designed search screen (this made it even slower). Also, I couldn't find any start screen customization options at all through the start screen search. This isn't a huge deal since I have Launchy for searches anyways, but then I noticed it renamed all of my chrome app shortcuts to "chrome.exe" and it blocked avg from working. I tried to reinstall avg, but for some reason wouldn't let me download anything from Chrome anymore without "free download manager" installed. I tried to use a restore point to erase the Windows 8.1 update, but it wouldn't let me even when I disabled all antiviruses and used the advanced restore option. I ended up just doing a clean install of Windows 8.0.
Normally, I would stick with it just to figure out why it was acting strange, but I have finals coming up, and I don't have time to mess with a beta operating system. I like Windows 8, and 8.1 will definitely add some great features, but I'd still suggest waiting a little bit for the bugs to be worked out before upgrading (unless you have the time and are interested in that stuff).