Yes... this is all very "unfortunate" (to say the least).
I haven't tried but maybe there is a workaround (again to say the least - it is more like a hack ).
During my tests (I think) the IAP engine returned the list of "restorable" products based on previous purchases even on the production server. If so, one could rely on that information to detect that the user has already purchased your content - note that if you call the restoredproduct it will fail so you need to decide/act based on the list of restorable products. I can't remember how much I tested it but it was something I considered that this could be a workaround.
Every day I have less hope that Nokia will actually fix the issue with the production server. It seems that they believe that the behavior with the test server that is actually wrong - I REALLY CAN'T UNDERSTAND!
Until then, unfortunately, IAP will be a single act for me and if and when I have to update my application I will most likely just give it away for free so I can save myself from reading angry e-mails from frustrated consumers