It's OK to be disappointed with the MBA. To each his own.
I'm not a big fan of the entire Macbook Pro line. IMHO, wildly overpriced relative to the upgrades from a Macbook, heavy, and the 17" is a freakin' aircraft carrier to lug around.
Ultraportable to me means anything under 4lbs, and significantly smaller than, say, a Macbook in one major dimension. I think we're all having trouble with the 'ultraportable' label, because most prior lightweight machines achieved that through reductions in length and width, defining the category.
For myself, what I want is a full-size keyboard and screen (my Macbook is an OK, but smallish screen, and great keyboard), and not much else. I need enough hard drive to carry some documents, and hold a few applications, but honestly, I could probably fit into a 20 gig drive if required.
I'd been trying to live off my iPhone when I travel, but the reality is that I just need more screen space and a real keyboard to do real work for more than a day or so. But the overall capability of the iPhone covers my away-from-desk needs quite well - it's just the input/output becomes a hassle for heavy use.
Similarly old G4 867 12" Powerbook handled my laptop tasks just fine with 640MB of RAM and a 40Gig hard drive. A 1.6 C2D CPU can handle the load just fine. I'm happy to toss the external optical drive into my checked luggage, just in case I need it.
Long story short, MBA meets my needs perfectly so far (though battery life could be better...). It's all the performance I had in my Rev A. BlackBook, in a package 60% the size. It is indeed a little pricey, and moving it from $1800 to $1500 would make it a no-brainer.
It's not for everyone, but an awful lot of people use their laptops like I do - email, MS Office, web, and an occasional dip into Photoshop/InDesign to make minor changes or do basic documents. MBA is a terrible choice for an only machine, or a road production machine, but it's an awesome 'real screen and keyboard in a minimum package'.