I made a wonderful, lightweight hat in Sanguine Gryphon's lovely Sappho yarn (laceweight merino singles). And I have lots and lots of the yarn left. It might take longer to knit thinner yarn, but you really can't complain about the mileage for your money!
(I cast on 180 stitches on US #2 needles, and knitted for a couple of weeks before starting the decreases....)
I took a few quick photos last night when I finished it. This will become the hat that I live in. I barely notice it on at all.
Now to figure out what to do with the abundant amount left. I'm going to probably make some sort of gloves...