The basic, fundamental issue, in my opinion, is that APPLE decided what they considered important in the design versus asking their customers.
They decided that they weren't going to compromise the screen and keyboard size, and defined ultraportable as thin and 3 lbs of weight.
To meet that, something had to be compromised, so goodbye ports, optical drive, use an iPod hard drive, etc.
The problem - many of Apple's loyal customers looked at the 12" PowerBook as a great size, and wanted a current technology replacement for that. Take away an optical drive and make it external, thin it out a little, and give it that Powerbook form factor, along with the current crop of ports found in other laptops, and I think many, many people would gladly hand over money to upgrade their PowerBooks. That design would also still attract a whole new group of customers looking for something thinner and lighter than the MacBook or MacBook Pro.
So, Apple comes out and says "we created the world's thinnest notebook" and alot of customers are saying "so what - its not what I want. Too many compromises to get that sales moniker"
You can easily dismiss them and say "if you don't like it, don't buy it." How does this help Apple? They just lost a potential sale from somebody who WANTS to buy a product from them, if only it was the right product.
The Air is creating a lot of controversy simply because there are customers who have their own design ideas on what constitutes an ultraportable, versus Apple's own ideas. A little bit of communication up front on Apple's part to talk to their customers to find out WHAT'S REALLY IMPORTANT TO THEM would've produced a laptop that got much broader market acceptance on its introduction, in my opinion, and created an instant hit. Instead, they get division and controversy.
How is this good for the Air and Apple?
Yes, they missed out on some sales from the people who were hoping for a 12" MBP. But the people who wanted that still aren't the only market for small, portable computers. Apple also opened up the idea of an ultraportable to people like me--those who never wanted one before, because the undersized screen and keyboards on them were too restrictive, and never used the ports that the MBA doesn't have anyway.
Apple gave its own interpretation of an ultraportable, and offered us something other ultraportables don't. For people wanting the same old ultraportable they had before, that sucks. I know. But for those who like the new spin on the idea, it's great.
Personally, I hope Apple releases a 13" MBP. 12" is just too small for me. The choice between a 13" MBP powerhouse and a freakishly thin, portable MBA would be a hard one for me....