However after buying and installing it on one iMac I went to my other iMac which I impatiently installed the GM on last week. I went into the App Store and clicked the Purchased button and to my surprise it said installed and I thought all was fine. But I then went to the Lion App again in the store clicked on the "Buy" or "Install" button (I forget which it said) and I got an error stating that my version of Lion was not installed from the App Store. Now that may not be a problem. I think I have seen a similar error when attempting to reinstall an iWork app I originally installed from CD.
So I think I am fine, but perhaps my Lion updates will come via the Software Update process rather than the App Store. This will obviously be supported as we hear now that Apple will be selling Lion on a USB stick so it's not a App Store ONLY thing.