Battery
Most people are troubled that the battery usage time they get is drastically less than what the manufacturer claimed. Most of the time, when a manufacturer listed the battery of having 4-5 hours, users actually get about 1.5 to 2.5 hours. The reason is, manufacturer listed the time "under ideal condition", which means turning the screen brightness to the point you almost can't see what's on the screen, sporotic/intermittent use, minimal disk activities, and so on so forth. Most of us actually "use" the computer, which is quite different from the "ideal condition".
Also, in order to get the list price low, the standard battery is 3 or 4 cells. A top line battery has 9 cells.
I have been buying extra ac adapter for every laptop I'd purchased. The battery is only for backup if powerful fails, and in rare occasion when I was waiting to board a plane in the airport.
Do you know that the mileage sticker on a new car is the mileage they get from Phoenix AZ to Los Anagels? That stretch of road is like coming down a slide (Phoenex is over 1,000 ft above sea level). I can go on and on about the lies manufacturers of various products made unrealistic claims (the life of CF bulbs, another good example).