It was a great episode, no doubt. But compared to some of their all time best episodes (the ones on New Caprica, last season's finale, etc.) I have to conclude that it was rushed to be finished before the strike started. Watching it again and since we don't see any recognizable continents on "Earth" I'm thinking it's not Earth. The destroyed cityscape reminds me of the classic BSG episode "Greetings from Earth" and also how, in it, they kept thinking Terra was going to be Earth and then it wasn't.
It's interesting to think that, thanks to the writer's strike, this cliffhanger was meant to act as a series finale if need be. If the strike was more devastating or if Sci-Fi totally walked away from the show this season then last Friday's episode would stand as the end of the show.