Although I'm not totally buying the whole Olivia-Peter thing. It didn't feel very in character to have Olivia give the big "you belong with me" monologue...
But very good episode overall, with William Bell blowing some stuff up before sacrificing himself. Very cool.

But Bell's role is a bit confusing to me... he says he was working with the alternate governement to keep tabs on Walternate and his evil plans to destroy our universe, which somehow involve Peter and a big brain sucking, eye exploding machine. This was why the shapeshifters were sent after Peter, this is why Olivia had to prevent Omega-head's head from being found and re-attached. It's all very convoluted just to prevent Peter from returning to the alternate universe. Couldn't Bell, who is clearly quite willing to let the ends justify the means, just have had Peter killed?