I had your dilemma. I have a 27" i3 imac and wanted a laptop/portable machine that i could use round the house/in bed. I tried an ipad but i find them so awkward to use having to hold in hand, type in the other. Yes, I tried the case on it as well but it just wasn't the right angle.
I since got a 2010 13" air, very nice, so much so my girlfriend downgraded from her 15" pro to it and I then....got an 11" air and i don't regret it for a second. It looks tiny, but you'll be surprised how easy going it is. Starts up rapidly, everything is sharp and snappy, and there's plenty of screen space, not to mention the wow factor when people see it!