This was an interesting little episode - but there were a couple things about it that keep me from rating it any higher than just "fair." The first is that it was so obvious than Alison wasn't going to stay dead. Even if it weren't for the fact that the show has been renewed (which means she HAS to be around for that,) the way the episode started would have been a dead giveaway. Every episode of the show starts with Alison having a dream and waking up before the credits roll. In this case, there was no wake-up, so it was obvious that she was still dreaming. That just killed a lot of the tension, and drained any emotion from what should have been the shock of Devalos dying as well.
My other problem was with Alison, herself. Yes, Alison has always been a bit of a neurotic mother, but she's also generally a very sensitive mother - one who cares a great deal about what's best for her children. The idea that she would keep pushing Ariel to work on criminal cases - to the point of acting like her schoolwork is almost an intrusion - is really out of character. Sure, Alison cares about her crime fighting and about the lives she's helped save, but I simply can't see her pushing Ariel to stay in Phoenix solely to work on crimes there.
Topping it all off, the way Patricia Arquette was acting tonight, her voice was really screechy - it was kind of annoying. I suspect it wouldn't have stood out as much if Alison hadn't been written so far out of character, but combined with the other things, it really cut into my ability to enjoy the episode.
That said, though, the story itself was interesting, and Mary-Louise's scam was a nice twist that I hadn't seen coming. And I'm very glad that the show is returning next year. It's been a favourite of mine since it debuted and continues to be something I look forward to every week. One week episode - even a weak season finale - isn't going to trump that!