Two items: last night Apple seeded another build of 10.6.6 (we reported a build had been sent back in November) build 10j537, and a Mac App Store statement from Apple has put the kibosh on any demo apps.
More intriguing is this bit as reported by Macstories, wherein developers are encouraged to host demos, trials and the like on their website. Presumably developer websites listed in the Mac App Store will lure buyers to the site, where they can download a demo. Then they'll come back to the Mac App Store and buy the full version. It'll be interesting to see the numbers when this all shakes out. In any case, the Mac App Store is coming sooner, now that January 17, 2011 deadline is looming.