I've been so in love with my West Elm linen/cotton duvet cover and pillowcases, that I ordered a 100% linen fitted sheet just now. Kind of a splurge, but will last a lifetime (and made in NY!)
I have read numerous articles about the wonders of linen: durable, moisture-wicking, dries faster than cotton, helps regulate body-temp, promotes a better sleep, and increases in softness with age.
My duvet cover wasn't wrinkly but I did pull it out of the dryer immediately. I'm not really concerned about wrinkles since it will be under the bedding and pillows.
I've read that some people hang dry their linen sheets and the weight of the fabric helps unwrinkle it.