I didn't skip the iPad 2 for any one specific reason. There was simply not enough that made me think that it was time to toss in a few bills for another. I never intended to re-sell my first iPad because I'm real excited to turn it into my kitchen gadget. The jump from 1 to 3 is similar to how I felt going from the iPhone 3G to the 4s. It is worlds apart in speed, display quality, and form factor. I don't get the lady boner over the retina display like everyone else seems to but I can certainly appreciate it. I am also looking forward to a speed bump. While the iPad 1 is still proving highly capable for me (hulu, netflix, web browsing, porn, twitter, e-mail, etc), I do believe that apps are starting to lean towards the need to have the better processor.
I stick with what I've always said, for the iPad, I would likely sit on a every other year upgrade schedule.