API options coming in November apparently. Should be very useful for my project that I started off a couple of months back. By useful, I mean, actually makes it feasible...
Some links:
http://paymentsviews.com/2009/07/24/paypal-adaptive-payments/
http://transfs.com/blog/2009/07/27/paypal-announces-adaptive-payments-parallel-payments-and-chained-payments-functionality-via-api/
http://www.pcworld.com/businesscenter/article/168040/paypal_to_open_platform_to_thirdparty_developers.html