Is recovering upgrades finicky and unreliable? The only app I can think of which has the functionality is Ascension: Chronicle of the Godslayer [0], and it's pretty clear and seems to work quite well. The UI isn't easily confused with in-app purchases, although you do have to go to "In App Store" from the main menu. Once there, you click Recover and it just works.

[0] http://itunes.apple.com/us/app/ascension-chronicle-godslayer...