Re: I hope they've done something about the keyboard
I moved to Mac with exactly the same model (2010 MBA, 2.1GHz, 4GB, 256GB SSD). It was very expensive at the time but, as you say, it still performs well. Every so often I consider an upgrade and I may go for the new model this year just to get the extra battery life. After 4 years of use (my business laptop - it has travelled more than 250,000 miles) it still works extremely well, the battery is not performing as well as it did originally but otherwise it is fine. I don't share your concern about the keyboard, mine has stood up well to 4 years of work and travel - I would like to have the backlit keyboard that the newer versions have however.
All in all, a great investment - I have never owned a laptop before this that lasted more than about 1 year, perhaps 2. Despite it's frustrations, OSX is far superior to the MS OS' that I have used for the last 10-20 years, I almost feel foolish for not switching sooner but I also think that the 2nd generation MBA was the first version that really nailed the performance/portability equation. The fact that it is Unix based is also nice as it gives me access to all of the usual command line tools that I need without having to install something like Cygwin.