I find the simplicity nice: find an app I want to buy, click buy, and I've got it. Developer just pushed an upgrade? It installs automatically without my having to do anything.
And the developer doesn't get anything, no matter how much work developing the upgrade took.
I agree that's a problem and would be very happy to see native support for paid updates added to the MAS instead of the hacks developers are currently stuck with. I didn't say the MAS is without downsides (the original article does a good job of spelling them out), but joesmo is arguing that the MAS has no real benefits to the user. I don't think that's true, and that's why I really hope Apple fixes these issues instead of letting the exodus continue.