I haven't personally, but I'm not impressed with what I see. So far, I'm sticking with Win7 until something better comes out...
I know that tablets are increasing in popularity, but the PC isn't dead yet... maybe in the next 10 years, but not now (and from what I'm aware of, Windows 8 is supposed to be geared towards tablets as well--from what I've read, that an ARM processor support).
I may just do what I did with Vista--wait out the storm until something better comes along. After all, as it seems over the past 10 years, it looks like MS is releasing a new version of Windows about every 4-5 years (at least from XP to Vista to Win7) so I don't mind using Win7 for another 4 years or so (I've been using it since its came out and haven't really had many concerns with it).
Long story short, I haven't tried the beta, and probably won't other than to see what they are proposing... but I don't think I'm going for Windows 8 even with it does release. I'm also not a big fan of cloud-based storage, which I guess Windows 8 is pushing more and more.
I guess I haven't seen enough added features in Win 8 to justify the purchase... Win7 is just now hitting its stride in the market, and I don't really see many benefits for PC users, except for those that want a more simple, smart phone-like interface that is easier to use. As long as MS keeps supporting Win7, which I think they will for at least the next 5 years--probably longer.
I think Windows 8 may be another Vista again.... Just like Windows Me was an early attempt at Windows XP. Like someone said, every other one is a good OS, and considering Win7 is probably the best out there now, I except Win8 to be less than impressive. Hopefully the next version (After Windows
will be worth the wait, and have enough benefits to merit an upgrade, because at that time, Win7 will probably be quite aged and due for replacement...