"So what can we take away from Bilski? Well, besides Justice Stevens’ 47-page tour-de-force concurrence arguing to uphold the historical exclusion of business method patents, here are my top four: (1) State Street Bank’s “useful, concrete, and tangible result” test is dead.
(2) Abstract ideas likely include “basic concepts” and methods that can be reduced to a mathematical formula. (3) Parker v. Flook’s “field of use” and “postsolution activity” limitations are alive and well. (4) Expect more Section 101 challenges, especially at the early stages of patent litigation."
(thoughtful analysis, quite worth reading)