For now it will do, but if you are able to spend it, get 4Gb. I did to buy myself some future-proof assurance (if not that, then just for ease of mind)
If you plan to have your MBA longer than a year or two, it will make your life much easier having 4Gb. There are upgrades to the SSD, but the memory can't be upgraded in any way, so you're stuck with that and 2Gb isn't that much these days, let alone in 3 or 4 years.
Then again, if you plan to do just safari, mail and perhaps some MS office in the coming 4 or 5 years you're using the MBA, it will probably do well now and with the future OS-X Lion or MS office 2014. And quitting apps when you're not using them helps to keep memory available as well.