for $3,000, you might as well get a mbp max'd out. sacrifice a little portability in order to get features up the yin-yang.
That's a good point -- didn't think about that, I just saw the MBP as less expensive. I'm gonna play around with the customization of it and see what I can come up with!
To answer your question and cut through all the subjective opinions around here:
Yes.
None of the applications you list really utilize the graphics card, which is the area the MacBook Pro is far superior in. All of those applications work GREAT on my 2.0 GHz Core Duo MacBook (not Core 2). Since the Core 2 is ~10% faster, a 1.8 GHz Core 2 Duo should be equal to my 2 GHz Core Duo...
So a 1.8 GHz MacBook Air should be almost identical to my machine in performance (I too have 2 GB of RAM), except you ALSO have the solid state drive.
You'll want an external drive if you're working with any large files, and that's a pretty big disadvantage. But in terms of performance, you shouldn't have any problem, as long as you get Photoshop CS3 to get the universal binary.
Trust me, an Air will be fine. I run Photoshop and Illustrator CS3 on my 1GHz 512MB machine all the time, and yes, while it's a little sluggish at times it's hardly what I'd call unusable.
Your income better be high enough. Personally? For what Apple is giving me for the MBA I will gladly get another L lens for the money.
As for your question regarding the 1.6Ghz or the blazingly fast 1.8Ghz option... Hmmm... that's such a tough question to answer... The truth is they both suck!
Technically speaking humans have been using Photoshop since the days of 600Mhz computers so I am sure you will do fine. It is just time spent waiting. And waiting. And more waiting. But I imagine the Macbook Air is going to run applications like Aperture or even the new shareware application Pixelmator so very fast with its great GPU.
Plus, with a 64GB drive you can hold so many RAW files. All of which can be speedily backed up through a USB2.0 connection! W00t!
I am making too many assumptions about you, for one thing you might prefer to be a "green star" and shoot fully auto all the time, but I digress...
I do not see how some of you guys are able to use the CHEAP revB screens for your PS work
I will never trust their quality regardless of the small size for any PS work.
So go get yourself a Dell:
http://thegadgetsite.blogspot.com/2009/01/dell-mini-9-better-screen-than-macbook.html
and we'll enjoy our 'cheap' MBAs.