I wrote a review in the store for the demo version. After writing the review, I visited the page for the paid version, and noticed that the store client acted as if I had the paid version installed. There was no 'Buy' button, but instead it presented the 'Launch' and 'Review' buttons. I don't know if this affects all applications with demo versions, but it's definitely something to take up with Nokia Store, as it could be losing you money.