For me it comes down to the fact that she is a very competent officer who doesn't let personal feelings get in the way of doing her job. Actually, the first of those two is all I need -- the second is a bonus.

I like her less for romance w/Lee. Romance with Lee is a very bad thing for both Dee and Kara, and the only person who has managed it without it warping her character is Roslin.

This is why I have come to hate Lee. (Also, the adultery. Also, the angst.)

Take Lee out of the picture, and you get scenes like the one with Dee in the raptor OMGsofullofsquee!