Apple MacBook Pros seem to have very inconsistent battery life, according to Consumer Reports magazine which did quite a bit of testing. The article below from CultOfMac details the results, but to say they were all over the place would be a good summary. Even the comments following the article (anecdotal, of course) mention a huge range of battery life times.
Since a portable device such as a notebook may depend on battery power a lot of the time, it's kind of a big deal. It's not clear from the article if this is a hardware or software issue (or both). It may be that one or two specific things are affecting the battery life, but again, that's not really clear.
Should be interesting to see how this develops and how Apple responds (if they do), since Consumer Reports is a pretty well-respected magazine.