the montbell ul wind pants are amazing! they are 2.5 ounces and pack up so small you will be grinning for like a week. of course, you have to pay to play with these-- they are among the most expensive. if you hunt, you can find them on sale though...
i use these in conjunction with the SMD gatewood cape as a shelter/ full-on rain protection. in other words, i put on the wind shirt/ pants under the cape when its raining steady and that protects me from rain that gets in under the poncho b/c of wind.
but having the golite wisp windshirt (2.5 oz, medium), the montbell ul windpants (2.5 with stuff sack, large, side note:sizing is small so go one size up), and the SMD gatewood cape i have wind and rain protection, a pack cover, plus a shelter for exactly one pound. o, the stakes add a couple of ounces.
but still, that is hard to beat.
i also have the reed pants. they work well in rain. they are definitely a thicker, less breathable material than the montbells but will repel more rain before wetting out than the montbell pants. of course, they are double the weight.