My wonderful baby A is now 6 months old, and she's certainly in the over 50% of babies who don't sleep through the night at this age. In fact, she wakes almost every sleep cycle to see where Mum and Dad are. If she's laying next to us she might fancy a quick bit of milk, or she may only awaken enough to place a hand or mouth on my breast, and then fall back to sleep. Occasionally she will only awaken enough to see where we are then back to sleep.
Yes, this is a bit of a pain in the ass some nights. If me and DH are watching a movie or something it can take three or four shifts, but eventually it will sort itself out. When she grows up and leaves home I'll remember laying in bed hugging my daughter, not watching 'I Am Legend' without any breaks.