I am the original poster of this thread. I got my MBA 13" Ultimate this morning, and after having been pounding at it for the whole day, here's my opinion:
this thing rocks!
It runs Photoshop, DreamWeaver, FTP, video and everything a web admin (my job) might need flawlessly. It's fast, super quiet and cool, no noticeable heat or fan noise whatsoever, battery lasted 6 hours of real WIFI use (internet browsing and email), and it's crazy light (perfect for couch surfing). The superior screen resolution (1440x900) helps a lot bringing more real state to the table. And the SSD is blistering fast!
This is simply the best laptop I've ever had. I cannot believe how well it runs my applications despite the "theoretically inferior" C2D processor.
So, to answer my own question at the beginning of the thread:
Yes, the MBA 13" Ultimate can indeed be used as my sole computer