I just wanted to mention that if you have a very small coop you can use newspaper (just change it daily, lol). There are some folks on BYC who just do that as part of the daily care. If you get a newspaper that is a free way to go.
For the nest boxes you can use shredded paper (from a paper shredder).
Pine needles sitting on the ground will be damp if you have had rains. Chickens are very sensitive to molds, so I wouldn't recommend replacing your dry current pine straw with some from the ground unless it is very dry.
I recommend pine shavings if you cannot reach into the coop easily to change out bedding often. DE mixed into the shavings is fine, but mine still got mites even with that (I wasn't dusting the birds at that time). It is true that it is dusty. I used it sprinkled on the floor for awhile...a long while...and I thought I would cough myself into oblivion until I figured out to hold my breath.
I switched to sweet PDZ to keep the floor dry. I like it better since it is much less dusty (the powder, not the granules). It is a horse stall refresher.
They need a litter to turn the poo into so that it is not sitting on the surface, or you could use something that you change out all the time. I myself chose to make the whole floor of my shed coop into a poop board and sprinkled sweet PDZ every day after scraping all the poo up. This will eventually ruin the floor, but I found that I had an incredible mite problem every time I tried to use pine shavings as litter (deep litter method). This will not work during the 10-20 degree weather we get for a short time and I had to wait for it to thaw.