WildHobgoblin: I purchased something about an hour ago, and the email was in my inbox literally minutes later. Might be something has gone wrong in your case.
aghem: I haven't received the Rebel Galaxy too - I also ordered something almost a 24h ago. Can be that they fixed the issue for new orders and now are working on the ones completed before the fix?
Seems likely, yeah, but I obviously have no way of knowing for sure ;)
I think they put that "be patient" disclaimer up so support wouldn't get swarmed with requests while they have a lot to deal with already. So while you might want to contact support, it's probably not a bad idea to wait a little longer. You're eligible for the game, and Gog will make this right sooner or later.