Definitely a weak episode, compariatively, but then there are always weak episodes (Absorbaloph anyone?) Regardless, it was executed fairly well, with some good touches. Unfortunately, there was a big hunk of cheese too.
Also, I feel I should point out, since no-one's done so yet (that I saw) the Da'leks in disguise were referred to as Iron Sides, not iron sights. It's a simple reference to their armour.
The only real problem with the series is that the big ending threat is obvious this time. There are cracks in the universe. BANG episode one, the threat is revealed. True we don't know what it is, or why they're happening, but we know they're significant in some way. Unlike Bad Wolf and Prime Minister Harold 'The Master' Saxon. Both of which were hinted at repeatedly, but never had any real attention drawn to them, or had their significance revealed until the final episode.