Both felt decently speedy for launching apps, browsing, watching quicktime trailers, etc.
I have a 17" MacBook Pro and have been wanting an "iPad-plus'' since the iPads were announced, something that could do most of what my 17" can do, but in a more portable frame.
I know there are a lot of disappointed people out there, looking for power and small size combined - well guys, it just doesn't exist yet. These new Airs are clearly out there to augment what you already have, not be a primary computer. I agree that the lack of a backlit keyboard is disappointing, but as a touch-typer, this is by no means a deal breaker for me. Everything else, spec-wise, is absolutely adequate for the use these machines are intended for.
For me, the 11.6" is the perfect companion machine to what I already have - a beautiful, svelte machine, which has ample processing power for most standard computing tasks, and if I need more on the move, I can always lug around the 17" big brother.
There is no doubt these are great machines, for what they are. I'm no pro-user, but I'm totally sold. I ordered an 11.6 with 4gb ram and the 1.6 processor on the spot.