As I've said here many times before, there is no meaningful category of invention called "business methods" or "methods of doing business" in US patent law. Of course, my views tend to be out of the mainstream. However, in this case, my views on the matter were pretty clearly vindicated by the CAFC in State Street.
Here's my quick take on Bilski. Note that it was quickly thrown together; I might temper my perspective upon further reflection.
Bilski is no big deal.
First, remember the source -- Board of Patent Appeals and Interferences (BPAI). The only lower authority of patent law is the examiners themselves. Even district court opinions (which are next to meaningless except for the parties involved) carry more weight. How often has the PTO (even it's highest officers) gotten patent law wrong? ALL THE TIME!!
And, as far as I can tell, the USPTO has an agenda to weaken patent protection as much as it can -- particularly for computer-implemented inventions. I see the Bilski opinion as advocacy by the USPTO.
Second, the BPAI expressly limited it's opinion to methods that are NOT performed by any machine (e.g., a computer). I think that you're asking for trouble any time people have to read a contract to determine whether they infringe your patent. I'm not completely convinced such is ineligible subject matter under S 101, but I dont' think anyone will allow such a patent to stand for whatever reason. Contracts have been around for ever and the "prior art", though extensive, isn't easily searchable. I think Bilski was a case like that, as I recall.
The claims at issue in Bilski could have (and should have) been rejected for any of a number of other, perfectly legitimate reasons -- vagueness, novelty, obviousness, etc. For whatever reason, the PTO chose to make the case about something else. My guess -- making the case for vagueness, anticipation (lack of novelty) and/or obviousness would have been more work than the Office would have liked (for the Bilski case and others like it). Having a nice threshold filter would make the PTO's job easier by dismissing a good number of applications as "out of bounds."
Has Bilski changed the way I practice? Not one bit.
Regards.