The most I'll be doing is Photoshop work with a fair few layers(but nothing overly complex)and quite a bit of photo manipulation, possibly in Aperture. I'm thinking that I'll be expecting too much of it, what with driving a second 24" screen as well.
Regardless, it's nice to see genuine and thoughtful observations on the A's real-world usage from all of you, and I'm glad you're all so happy with this machine that is all-too-often utterly written off.
Be well.
I've been using my Air for Photoshop - again, nothing complicated, currently working on a web site that's 4.8mb for all the graphics in the file. I generally have iTunes, FireFox, Safari, MSN and Text Wrangler open at the same time - no problems. I've not used Aperture so couldn't comment.
I did connect my 24" monitor yesterday whilst doing some edits of CSS - keeping the code on the Air's screen and the site on the 24 whilst watching TV using Zattoo, all worked fine. The fans did come on, but I'd expect that. I didn't notice any slow down.
Not yet tested Parallels with it, as I've not found the time for the install and setup.
I had the same doubts as yourself about using the Air, I like to keep everything on one machine so it's just there, whenever I need it - splitting files onto two machines has never worked for me. Having the 14 day return policy gives you two weeks to test drive one, after 2 days I think it's much more likely i'll see the whitebook hitting eBay than i'll be sending the Air back.
One thing that I have found - the screen really helps out in Photoshop, I wasn't able to see the subtle differences in gradients on the macbook, but on the Air I can - maybe it's my ailing eyes!