God, yes, the Google Market 15 minutes is bollocks. One notepad application I purchased to sync with my Google Docs took 3 hours to "authorize" my purchase before the app would work, and after that I was well after the 15 minute mark. Fortunately, I ended up liking the app, but otherwise it would have been such a waste.
I'm also frustrated that there seems to be no way to delete an app from one's Market list after it's been bought. Without getting too triggery, I have a "pregnancy tracker" app that I will never ever use, and I would prefer not to see it every time I open my Market list.