I used to chill, decant, then let the starter come up to the wort temp before pitching. A couple months back though, Denny mentioned just pitching it cold, so I've been trying that method since. There has been no noticeable difference in lag time, attenuation, flavor, etc. due to yeast performance. It's just my experience, and there's nothing wrong with letting it warm up, or adding more wort, etc., but I find pitching cold to be far more... pragmatic...