I think it would depend what said person used the powerbook 12 inch for. If you just appreciate the small form factor to carry around, take notes, work on documents, etc, I think the Macbook Air is great. I mean you can't complain about it's performance: it's still probably 6x faster than those slow-as-hell G4 chips. But if you needed a full feature computer, then the MBA would not cut it since it obviously lacks certain things. In my opinion, though, I do not use firewire and I plug everything in into 1 single USB port and use external speakers as well. I could see myself using it as my main computer, only if they put a bigger (160 gig) hard drive into it.