I thought it was an intriguing episode that worked for the most part, but only gets a good because of the seriously, seriously rushed ending.
I liked the Cubes, though. The idea of a slow invasion that everyone would take for granted and then something that would catch people's attention was great. I thought the character moments were really nice - especially between the Doctor and Amy. Really my only complaint is the ending. I'd hope the Tally will be revisited or else it would be almost completely pointless, but it was certainly sudden and easy.