What’s your criteria for adding to your blogroll?

I received an email last week from a CU vendor that recently launched a new blog and they are trying to get it off the ground.  They asked me to include their blog in my links section and I decided to think about it over the weekend.  I’ve heard the name of the company before, but I wasn’t that familiar with them.  Their site looks great, they’ve got good content in their blog for the niche they fill and they seem like nice people.  But what ultimately makes you add someone to your blogroll?  Quality contributions in comments around the blogosphere?  Good posts on their site?  Pretty mug shots on Twitter and LinkedIn?