I like to talk smack about Apple, but they've just added a new feature to iTunes that lets users apply credit for a bought single to the purchase of the full album. That's good and just a tad bit revolutionary - back when you bought the Beastie Boys "So Watcha Want" maxi-cassette for the Cypress Hill dusted remix, you couldn't get credit against the album.
Strings? There may be some that pop up, but right now the only reported one is that you only have 180 days to take the credit. If it takes you more than half a year, well, you probably don't really need to buy the album.