Have there been some funky workflow issues to tackle? Sure. But they've gotten better over time as apps and iOS have evolved for the better (thank god for Goodreader...) and I have no doubt at ALL that they will continue to evolve for the better.
For me, the lifesaver was FileBrowser. It lets me connect to any shared drive on the same network as the iPad, and download and upload files to and from my iPad. It's taken a few steps out of my workflow. For instance, when I get a mail with an attachment that I want to work with on my desktop, I can use FileBrowser to save it directly to the desktop from the iPad, instead of waiting until I get to the desktop and opening the mail again so I can save the attachment.
I think a centralized file system (or a version of iDisk which is MUCH more robust) baked deeply into/across iOS is really the final frontier, and I think it's coming in iOS5.
I really hope you're right.
I will NEVER go back. The iPad does basically everything I need to do, and does it well. And weighs much less than the next best option. Even the 11" MBA weighs 50% more. Yes, every ounce counts when you're talking about the ability to freely and without hesitation take your device basically everywhere...
For me, the iPad doesn't quite do everything I need -- I need to prepare busiess letters with some specific formatting, and they need to be in Word format. Any formatting I do in Pages have a chance of coming out oddly when converted to Word, so I need to do all final formatting on my laptop or desktop. Also, sometimes I like to see more of a document I'm working on than is possible on the iPad, where, with the onscreen keyboard up, you can only see a few lines at a time. But the iPad is definitely the right size for me to take on the move. As you say, even the Air is twice its weight.
But on the other side of the coin, the other day, we decided to go out to a cafe on the other side of the park, and since it's a rather long walk and it looked like it might snow, I left my iPad and took only my iPod touch. I immediately regretted it once we were settled in at the cafe, because the touch is just too small to sit back and relax with. The touch fits in my pocket, and is the best mp3 player I've ever had, but it just doesn't do as much as the iPad, and isn't as enjoyable for things like reading books and webpages. So next time we go, I'm definitely lugging my iPad with me even if it's in the middle of a hurricane!

Seriously, there are *some* situations where the ultra-portability of a touch or iPhone make them the only devices that will do, but for me, those situations are far and few between.