I have the Marmot Precip stuff, both the jacket and the anorak. I use the anorak (very light, only about 8 ounces) when there's less chance of rain. The waterproof/breathable fabrics have their limits...it depends how hard you're working and how much you sweat. I have some homemade Ultrex rain pants that work wonderfully, although everybody bad-mouths Ultrex.

A few years ago I spent my REI dividend and then some on a smartwool t-shirt and zip-T. Unlike most folks, I don't care for them. In warm weather, the t-shirt gets soggy and takes much longer to dry than polyester (though faster than cotton, of course). I like the zip-T better, but it's no match for my REI MTS zip-T.

I think the synthetics win hands down, and especially for wet weather.