I wear the PI shrug
http://i.imgur.com/D0hEh.jpg and LOVE it. The sleeves have little pockets inside that make it a mitten when it's super cold, but easy to pop back and push up as it gets warmer.
My ONLY prob with it was that I had my watch over the sleeve and couldn't have removed the shrug without taking off my watch. Good for cold, not good for cold-to-hot.
For sizing, I have a medium and it is a BIT tight on my out-of-shape 5'5" 140lb frame (though <3 the effects of tri training so far on toning my arms - better every day!)
Hope this helps!
-----------------------------------------------------------------
You. You make me stronger.