Just reading through the thread. My 7 week old dd sleeps 'through'. She went to bed at 9:30pm last night and I eventually woke her at 7:30am. My mantra is let a sleeping baby lie. She is not interested (at the moment) in being fed at night so waking her would be a waste of time.
She only cat naps during the day and nothing I do makes her sleep for longer than a 1/2 hour at a time about 4 times a day. But I won't complain. I prefer her to sleep at night because nothing makes me more irritable than lack of sleep.
She is only breast fed but seems to be gaining weight and is much much happier after a night of long uninterrupted sleep. When she was waking before, she just cried ALL day.