Something I've just spotted is some keywords are slowly drifting upwards, although I would have expected this to happen much faster for high volume keywords with double digit CTR's if it was simply a case of ad history having to build up again. Interestingly, all keywords marked down are still graded no problems for the three measures in the diagnostic box popup.
Something else I've meant to ask before is about people seeing QS of 8 and 9. I very occasionally see 9, I don't think i've ever seen an 8, and frequently a 10 becomes a 7 and vice versa, i just rarely see anything in between. Do other people frequently see an 8 or 9?