It seems that if you did the debug mode in the app store, and then used it to grab the pkg file out. It seems it wont allow you to install the updates for the App. App store wants me to repurchase 3.0.1 stating:
Server 3 is already installed and was not purchased from teh Mac App Store. Do you want to buy OS X Server 3.0.1?
Isn't that the case with all Apps installed using that method?
No _MASReceipt, no updates, i guess...
Edit: Wait, maybe i got that wrong - does this happen on the machines that you install the PKGs on,
or on the machine on which you originally downloaded the App from the AppStore?