A comment on the zip offs: Definitely make sure to buy some where the zipper is well above the knee. If not they a) make poor shorts, b) are less comfortable 'cause the zipper drags across your knee, and as has been pointed out c) you create a point of failure.

The quality name brand ones are more expensive, but sometimes you get what you pay for. The REI ones are pretty good. A lot of the time, if you wait, they'll put them on sale as a "loss leader" to get people to come in to the store.

While not a mark down, right now there's a 20% discount for all REI members. If you're not a member, you can join on the spot, and they'll still give you the discount.

A comment on BDU's: the heavier, temperate climate ones are really tough, but are warmer. One option is to get the heavier temperate climate pants and the lighter hot climate shirts. This is a good option if you're going to be firing from kneeling position or doing a lot of things where your kness will hit the ground. Also, the heavier ones are great in brush and resist snags well. The temperate climate ones are definitely not as breathable as the hot climate ones.

Here's an interesting link on BDU's: BDU Info Note that the army has now switched to ACU's.