My main concerns:
1. Higher res on 13" (
see topic)
2. 1.86GHz C2D on base 13" (only upgradable when you go all out)
3. Will it be cool enough?
Before I'd consider buying this, I'd like to know if:
1. If the text and such aren't too small. I'll be using it for a long time in the store before deciding
2. The flash storage will make a huge enough difference to compensate for the not-too-powerful CPU
3. If multi-tasking (10 apps minimum, many tabs in browser) works without problems
4. How much can it handle without the fan kicking in? I hate loud machines, and watching a flash or 720p video or doing some serious multi-tasking should be possible without much noise from the fan.
Apart from that, I think it's a great machine. I looks great. LED backlit screen. It's light and super thin. For 90% of all people it's enough for most of what they'll be doing every day. For me too, although I do need it for some serious multi-tasking from time to time.
Edit
Check out the hands on video:
http://www.engadget.com/2010/10/20/macbook-air-13-inch-first-hands-on/
That 11.6" looks pretty damn cool