I've always had/preferred the 11". I had a 2010, a 2011, and my 2012 will be here on Monday. I thought I had decided to get a 13" this time around, mainly for the battery life. But after looking at them again in the store and online, I decided the 11" was my favorite. I just LOVE how tiny it is. It's so much more portable, and since I travel by motorcycle a lot, it's easier to carry.
What I would love to come up with is a nice, slim hard case that would hold the 11" and my iPad together, and be waterproof. Like a Pelican box, but I kinda doubt they make one in that size. Then I'd be golden for motorcycle trips.
Rob