A good pad like an Exped Downmat is worth the $$$$.
Concentrate on layers of clothes vs heavier individual coats or pants; I like nylon fishing pants and layers of wool long johns as needed.
Carry a pair of cheap light pairing knives with the plastic 'sheaths' instead of a heavy knife. You usually can pick up a 2 or three pack of them at a Marshall for $5-$10.
Sawyer squeeze filters are very nice. I pack in a couple empty gallon milk jugs to fill up with a couple days worth of water so I don't have to filter everyday, and they are a lot easier to pour out of than the Nalgene bags.
Don't get caught up in gimmicks or 'neat' items. You'll just end up with more weight and probably won't use them.
Have a good attitude. BP hunting is tough but very rewarding.
