@Tomas J Good work and I put Kaju on my favorite list. Regarding sandboxed apps and updating them:
Well... still the best way is to put the app on MAS. The side-effect are 30%, review process and some restrictions... but all in all the user experience is preserved.
I very much like the App Store, because it brings in lo' o' dow. Sales that I would probably never have done on my web site, so I can live with the 30% cut and the tacky reviewers.
But yet, I do sales on my own sites, and I think the idea to have an autoupdate is a nice one. Adobe does a silent update, probably based on something similar to what Sam describes, but a lot of people simply download the installer where you want and let you run it. If Kaju supported installers, it could manage sandboxed apps.
@Sam R @Tomas J The side-effect are 30%, review process and some restrictions.
These side effects are actually causing some big named brands to drop the Mac App Store!
The big named brands may have a recognized image and advertising power that most of us will never have. That said, I wonder how many sales they probably miss by cutting themselves from the die hard App Store customers. Even the best known magazine still needs newsstands.
It is probably just as ill advised to drop the MAS than to send your web site visitors to the App Store instead of making the sale.