Grand Central Dispatch comparison/likeness?

AFAICT, Grand Central Dispatch is a nice implementation, with a few clever tricks/API, of age-old pretty-obvious ideas. And a whole lot of marketing that seems to be confusing people who aren't up on their details of concurrency models, and become convinced that there must be something *there* or Apple wouldn't make such a big deal out of it. (Honestly, the marketing and generated excitement is probably more effective than the API at achieving Apple's real goal of getting more app developers to take advantage of SMP; it's advocacy, not brilliant new engineering.)

(Though sure, "blocks" *are* neat.)