The disappointment, to me, isn't with the iPad alone. It's with the new move in the industry to non-upgradable devices and internet-dependent software.
I've enjoyed my iPad 1 since the day I bought it, and I haven't seen any need to replace it with a newer model. Neither the Retina Display nor the camera were particularly important to me, and I didn't have much need for more storage or memory.
Would I like to use iOS 6 on my iPad? Certainly. Do I need to? Not right now.
Over the next year or two, though, I'm sure there will be plenty of software that I'd like to use, but won't be able to. It's possible that some apps, like Netflix or Spotify, or some games, will reach a point where older versions won't work anymore, as they roll out features that require some update or another to play nicely with their servers.
What will happen if I have to restore my iPad to factory settings, or just accidentally delete some app? Will I still be able to re-install the version I need in two years, or five, or more?
Every computer reaches a useful end to its life at some point in time. The acceleration of that process due to a closed system that allows no upgrade to RAM or storage, and no ability to install software except through a centrally-controlled repository, frankly sucks.
Windows 8 shows that it's more than just Apple headed for closed systems. If current trends prevail, how far out are we from the closed model of the iPad being the standard for the industry?
I hope there will be some consumer backlash, and a company with a commitment to great technical and experience design takes up the standard of more open hardware and software as a competitive differentiator. I'd vote for them with my dollars.