They've been threatening it, pundits have reviewed it, I just downloaded it. First I clone my current Lion drive so I can go back if there's a disaster, then I install it on my MacBook Air and give it a runthrough. As always, I advise waiting a little while and check the Mac blogs to see how others are doing. So far, people seem to be happy although a few random incompatibilities are appearing.
I'll run it and let you know this weekend.
Here is a great detailed what-to-do from one of the Apple discussion blogs. This is the kind of thing I should write but have not gone into this much detail. Read and follow this advice when you do your own upgrade. This especially includes waiting a week before you do it!