I rarely use DLC, usually it's nothing significant enough for me to bother. Though I did get "Bring Down the Sky" for ME1, but that's 'cause the patch had it, anyway. Most of the DLC I've heard of never had anything interesting, especially nothing worth paying for.
So far only game I ever bought DLC for was Borderlands...but as of right now it was kind of pointless since none of my friends have it. Hopefully someone will pick it up soon so I can get back into it.