A question was asked at the Django Toronto meetup during the metaclasses talk, basically, "what would you use this for"... so, here's my talk on Metaclasses [pdf] from a PyCon of the Python 2.2 era, which addressed that question at some length (the first half of the presentation). It doesn't secifically mention the use-case cited in the Django Toronto talk (pre-calculation to concrete-ify a final class, as it is just glossed over as converting human-friendly to machine friendly structures), but it does cover most of the use cases envisioned back when Metaclasses were "new stuff".