I don't have a tip for cleaning up pine needles but I do have a pine needles mess horror story. A few years ago I was living in an apartment with four girls--two of whom were pretty messy. Around Christmas the two who were messy decided they were going to get a Christmas tree. Knowing exactly where this was headed I said I wanted no part of it.
Well of course I was right and come APRIL the Christmas tree was completely dead and still in our living room. Finally I put my foot down after many hintings and suggestions and said that it had to be taken care of.
One morning a few days later I woke up and, yes, the tree was gone. But there were pine needles and branches EVERYWHERE. Covering all the carpets and the entire entryway. Apparently one of the girl's friends had drunkenly decided to take the tree to the curb but of course did not also drunkenly vacuum up the mess.
Those pine needles stayed on the carpet for another six months until I moved out. Mainly because I refused to vacuum them up since I had previously declared that I was not having anything to do with the tree. (I am really stubborn.) They may even still be there today!