Can I update apps that I've already purchased through the Mac App Store? I've previously purchased several apps (Pixelmator, Rivet, a few others I can't think of now) that are now available in the Mac App Store. Given that apps in the store are not allowed to use their own updating frameworks (like Sparkle), how will I get updates to them in the future? Can I somehow tell Apple that I already own those apps and get updates through the store? Or will the individual developers have to work something out on their own?
From Daring Fireball:


  Panic on the Mac App Store
  
  Cabel Sasser on what it’s like for existing
  Mac apps that are now in the App
  Store:
  
  
    PS:  If you’re a current customer,
    there’s no way to convert a previous
    purchase into a Mac App Store purchase
    — that requires a re-buy. But
    remember, what you have now will
    continue to work just fine.
    
    UPDATE: The Mac App Store may show
    software bought from us previously as
    “Installed”, even though they’re two
    different licenses. You will not get
    Mac App Store auto-updates unless you
    purchase from the Mac App Store. To
    re-enable the “Purchase” button in the
    Mac App Store, just drag the app to
    the trash. Your preferences/sites will
    not be affected.
  
  
  In other words, for apps that use the
  same bundle ID for the both the Mac
  App Store and non-App Store versions,
  the Mac App Store will not install
  updates to already-installed non-App
  Store versions, but it will recognize
  them as being already installed. If
  you want to get updates via the Mac
  App Store, you’ll have to re-buy the
  app through the App Store.