When the final two contestants of season eight of "American Idol"—the folksy singer/songwriter Kris Allen and the zeitgeist-capturing vocalist Adam Lambert—faced off one last time, few predicted that the show's season finale would end with a controversial upset. Not even the winner himself.

"The past couple of days have been crazy," says Allen, 23, who appeared as stunned as anyone when host Ryan Seacrest declared him the 2009 "American Idol" May 20. "Things have changed completely . . . now that I'm the 'Idol' winner, I have to go out and impress people."

Though the chatter about Allen's victory over Lambert has been huge, with many believing Lambert will emerge the bigger star, the ratings were a bit tamer. On average, 28.8 million people tuned in to the Fox live broadcast, according to Nielsen Media Research, a decline of nearly 4 million viewers from the 2008 closing episode and the lowest season-finale rating in "Idol" history.

But despite the lower ratings, "American Idol" still drives sales unlike any other TV show. Five singles by Allen...

Click here for the full story including how the finalists' music sales fared after the season wrap, how sales for guest performers were impacted, the record plans in the works for the winners and more.