Looking past the plotholes and inconsistencies, Seaver with the observations no one else can make, and the general underuse of JJ in her brief return, "Lauren" is damn exciting and the episodes flies through the hour. We see the dark side of Prentiss as she tries to take Doyle down, and Prentiss hanging in there as Doyle interrogates her, while the team tracks down leads to find out what happens.
The great thing about tonight's episode is that it dispenses with what held back "Valhalla," the team in the dark about Prentiss's past. They figure out the truth early in the episode, so their actions in the episode are actually productive. The episode maintains a fast pace as Emily's scenes are frequently interspersed through the investigations, always with ramping tension between her and Doyle as more information is revealed.
The ending is kind of lame, but it's a symptom of the industry. The producers and everyone else want Paget Brewster back, but her contract allows her to find a new show. Being a smart person, Paget has been looking for comedy pilots and has signed up for one already. If that doesn't work out, however, the writers didn't want to leave her out in the cold, so they graciously left an opening for her to return. Yes, it takes a lot away the dramatic impact of her death (or non-death) and you can quibble over it as much as you want. But I can't blame anyone besides CBS, because that's just how these things work.