I hope this is another "fake Earth" like TOS had. Seriously, is it that hard for a show to have a quality happy ending? I mean sure, we've got a half season left over, but come on.
Regardless, I predict that the rest of the series will go downhill. And honestly, that symbol of "omg earth people kill themselves becausee of nuclear war!!" is so ****ing old it's not even funny. Not only is it not that neat of a device to begin with, but it's a massive cliche in series like these. All in all, this episode was awesome up until they got to Earth. Then it sucked.
What makes me even angrier is that I pretty much excpected something like this to happen.

Seems like every single absolutely amazing episode they make they have to add something in with about 2 minutes left of the episode to make it suck.
EDIT: Upon further reflection, I guess I overreacted to the ending. It didn't suck, par-se, but it certainly did piss me off. Was it in a good sort of way? I'll have to wait 6 months to know, so no, it's in the worst way possible.