I’ve been impressed with the battery life of my MacBook Pro so far. The machine does get quite warm, but I’ve never experienced excessive fan noise or the like. In any case, this is probably an important firmware update, though Apple hasn’t made information about what issues it addresses so clear.
Check out some info from Apple here: Battery Firmware Update
Update 4-30-07: Apple has come out with some more information about the battery issues addressed in the recent update. Apparently, Apple has acknowledged that some batteries may be defective. See more here: Apple Battery Issue