Yeah, I had a bard, and I shunned this spell. Since you only get so many that you know, it's definitely not worth it to take a spell that your bardic abilities almost completely duplicate. The only thing of value to the spell is the bonus against all saves, and really, that's not worth blowing a spell slot on.
Lingering song is the BOMB. It's a must-take bard feat, in my opinion.
BTW - Nightchill, inspire courage just lasts 5 rounds after you stop singing, so with lingering song, it's 10 rounds after you stop singing. The time it lingers is independant of the time you've spent singing.
That being said, just spending a standard action to start up inspire courage and then letting it ride for 10 rounds while you cast spells and do whatever else you want is pretty awesome. I was very effective as a bard... haste, inspire courage, inspire greatness.... the party would just rip through opponents with all that buffing.
-The Souljourner