Yeah, not pegging the axes at zero makes for a much more dramatic graph -- a classic way to lie with data viz. Sometimes it's fine to do that (e.g. because without scaling it's impossible to visually understand some of the data), but the context should be made clear.
That said, the plot of the Macbook Air's battery performance vs. the Macbook Pro's is really interesting. I haven't done the tracking, but this agrees with my anecdotal sense is that my 2011 MBP (likewise a main work+personal system) has had really excellent battery longevity relative to prior Mac/other laptops I've used.
