I still have my issued Gortex parka and pants. While they are excellent as rain gear and windproof, they don't keep you warm unless you dress appropriately underneath.
For a bit more then the cost of the military Gortex parkas and pants, I highly recommend Browning Hydro Fleece. They are unbelievable! I've used them up by Lake Erie duck hunting. If I can stay warm with those icy winds blowing from the Great Lakes with the hydro fleece, I know they work!
One last thing, the camo on the hydro fleece is much more realistic for winter and fall hunting then the military parkas and pants.