I wouldn't necessarily look for stats or studies about meta descriptions here, but look at research done on PPC copy as well. There is likely a whole lot more of it for one, and its a very similar concept. Which words get more clicks? That's what it boils down to. I'm sure if you look more for stats in the PPC side of things you can find more concrete sources on what language is most effective.

These techniques work just fine. Panda may have hurt the quality of these aggregators and directories, but they still pass link juice. I would probably not pay for it, but there are a lot of free ones, and if you have a blog you might as well submit to them as it is quick and easy.

Well this has never happened to me before, so I'm guessing a Google glitch is unlikely, as I use Google dozens of times each day and haven't seen this. Chances are its one of your other two possibilities, although I'm not sure how any type of cookie could cause this. Very interesting find, I would post it on the Google help forums as well to see what any of the Googlers think about it.