2010 13", 2011 13", 2012 11"
Got the 11" sometime last year about June, it's a real delight to use.
I actually carry it around a lot more that the 13". Meaning I use it more often as a portable computer than I ever did with both my 13" air. Battery life has not been a problem so far.
The main draw back is once you fall in love with the 11" it's really hard to consider any other alternative, kind of like how the 12" PowerBook was.
I went from a 2009 13'' MBP to an 11'' Air, then to a 13'' Air. Of all 3, I personally prefer the 13'' Air. The 11'' Air was really great to use, especially in certain scenarios, but after about 2 years of use I couldn't deal with the battery life anymore. It is easily the worst drawback for an 11'' Air and it's the reason I'd recommend against buying one for most users. Also, as easy as the laptop is to carry around, the screen just wasn't big enough for me to feel productive with using that laptop. Eventually, I caught myself using my 15'' every time since I couldn't have multiple windows on the 11'' open, which is why I've moved to the 13'' Air.
If apple threw a hi-res display with more real estate and more promising battery life on the 11'' Air, I'd probably get one again. But seriously, I was getting under 5 hours on my 11'' Air with only Chrome and maybe a text-editing program open. Under 5 hours!
LOL...How old are you? You had a 2009 MBP, right? So you KNOW what battery life used to be like? I have a 2008 MBP still humming along...maybe 2 hours unplugged (new battery last year). 5 hours in this small of a package is HUGE!!! Don't get me wrong...I'm ALL for better battery life...but it's ONLY been in the last two years we've gotten to the point of 5 hours of useful battery life in a portable...and one that weighs two pounds!!! Come on...give it a bit of time. It's definitely NOT Apple's fault...they've put the biggest battery in the Air that'll fit...it's up to Intel (Haswell's priority is energy saving) to provide more efficient and faster chips.
Seriously...that made me laugh. 5 years ago, we were lucky to get 2 hours unplugged from a decent machine