Someone (Engadget?) said they only got 3.x hours or something--until they lowered the brightness of the screen. These screens have brightness to spare, so that doesn't bother me. Of COURSE Apple's "up to" battery times are not at max brightness (but they are measured with WiFi on). So--turndown the brightness when you don't need it, avoid sending power to things like Bluetooth and lighted keys when you don't need them, and it seems like you'll get something like Apple's stated time.
CPU and HD usage will cause a lot of variation of course. Expect most people in most situations to get less than the "up to" 5 hours amount.