It really depends on the baby. Most seasoned parents would likely let the baby sleep and not disturb the baby. The reasoning being, 'If the baby were truly hungry, he would wake up.' Even adults wake up from hunger. Also, sleep is extremely precious to both parent and child. So by breaking the baby's sleep, you're screwing up a 'good thing' for both parties.
However, you really have to gauge based on your baby's growth and development. If you feel your baby is growing and thriving, then don't wake him up. But if you feel that baby could use the extra calories, either because of slowed growth, or low birth weight, or various other reasons, then you should definitely wake the baby up.
Formula fed babies tend to stay full for longer because its considered to be 'heavier' than breastmilk.
Last point would be to do what feels right to you. If you're waking up to change diapers anyway, or are unable to get adequate rest because you are worried about the baby not having eaten in several hours, then feed him.
If none of the above concerns are relevant, then rejoice in having a good sleeper and feeder on your hands and sleep the night away!