I think it's worth carrying an AFE or Pooley's guide with you, even if you don't update every year. Compared to the cost of an hour's flying...
I often use the web as a source of preflight info, but there are times I change plans during a flight. If you print out everything you might ever need from the web, you'll spend more on paper than on Pooleys. Personally I don't think it smart to surf iPhones in the air, unless you have a 2nd pilot.