I thought that wasn't too bad, really. There were a few moments when the urgency seemed to be sidelined by nice long speeches, like Martha taking forever to reassure the Doctor. Emma and I were both yeling 'just press the sodding button!' at her. Of course, had she done that she'd have managed to freeze the Doctor properly before the power got switched off....

Since you all seem to be expecting me to come in with a science rant, I'm probably going to surprise you by not really doing so. If one can accept that there is a giant spaceship crewed by humans halfway across the universe, it isn't a huge stretch to accept that there are shields that can protect the ship so long as it remains a certain distance from a star (especially since this one is apparently capable of mining stellar material), and that the countdown actually refers to the point at which the critical distance is reached and everything overloads, killing the crew and leading to the destruction of the ship. So no problem there.

The only part I did have a problem with was the attack of bad ergonomics and bad science combined in the scene where the Doctor is flailing around on the outside of the ship trying to remagnetise the pod. (I'm not even going to bother going into just how stupid it is to hide in the one part of the ship the murderer can actually jettison....). The bad ergonomics comes from having the controls to do that on the outside of the ship and not the inside, and then out of easy reach from the airlock, and the bad science comes from the buffeting the Doctor was getting. Space, even that close to a star, is near as dammit a vacuum. There isn't a great wind that would blow a person off the side of a ship, especially if he's supposed to be inside the shields (if he's outside them he's fried anyway). Why couldn't he just casually spacewalk across to the controls and then spacewalk back?

Shades of The Impossible Planet (even the spacesuits are the same, so possibly this takes place around the same time), some silly bits. How convenient that the Doctor adjusts Martha's phone immediately before she needs it randomly for some pub quiz question on which their lives depend....

Not bad, but not great. A nice slice of evening entertainment.