I'm pretty satisfied with my mid year 2010. I'm going to stick with it. I get a new iPad every gen so I won't be upgrading my MBA too.
I upgraded to a retina iPad and the difference is remarkable but not as "essential" as the iPad board would lead you to believe. To be honest, it leans more on hype than real world usage because in the end then you'll be able to see things "better" but won't necessarily be able to do anything "new". And if it comes with a huge battery hit then I can see it not being ready for this gen of MacBooks. But the reason I'm eager to see if it will exist is because it sucks to miss out on "new tech" because you couldn't wait a month longer.
The only reason I went for the 11" model is that it's easy to carry - it's not much bigger than an iPad - and has a nice keyboard. The screen's pretty good for it's size, also. Overall, it's the perfect size for an airline tray and hard to beat for those who travel or lug their laptop around frequently.
Ultimately, if you want a decent laptop you can carry around and use as your primary machine, I reckon the 13.3" is hard to beat. If you want something smaller than an A4 sheet of paper with plenty of power and more functionality than an iPad, get the 11.6" model.
I also want to use it professionally. BUT i'm looking at this screen for like 6 hours a day and i wonder if that is big enough.
I don't own the 2011 model personally, I have the 2010 one, so I am definitely looking to upgrade.