Jimmy Smits was terrific in Season 3 of Dexter playing a d.a. with a dark side--much like Dexter's 'dark passenger.' Smits powerfully portrays the d.a. with a huge ego. He's charming, seductive, and ultimately dangerous.
The storyline with these two damaged men was superb. Miguel finally gets Dexter to open up and chill with him; it's good to see Dexter relaxing. We think Dexter will finally have a friend who understands him completely, but unfortunately it is not to be in the long run.
Smits should win an Emmy for his role. I'm really sorry he won't be in Season 4--I'll miss him.