I don't know, I'm reluctant to thing is just a problem with the battery, there are nearly two hundred posts here about this issue and I am sure much much people is having the same problem but just went and bought a new battery, and didn't think to check forums, so I don't think is just a coincidence.
Apart from battery calibration, yes, it's true most of us run from the mains most of the time, but I am also sure I unplug every often the cable until the battery runs off, have been doing this until I installed Snow Leopard. Problem now is we can't even calibrate again as computer will shut down before.
Here is a thought, I think most of our Macbook Pro are about a year old, therefore the battery is not in his best health, then it comes Snow Leopard, it seems from other people posts that some times it gets very hot and uses the fans at high speed, is it not maybe some faulty within the OS and some hardware combination, that makes it to use more amps and somehow can wear out the battery faster than usual?
What worries me the most is not only the lack of duration but the way it shuts down with no warning, first time it happened to me I nearly lose some info, hopefully I didn't, but I use the laptop to work, so is not good.
Anyway, I think is best to wait until there is some resolution about this issue before buy a new battery, maybe Apple comes up with a new update soon, as they did with 10.6.1