It was quite good, though the whole "end of the world" plotline seemed a bit uninspiring to me for some reason. John Simm played the Master well, I liked his performance, and his choice of companions.
Also, im afraid I have to point out that those weapons would've shreaded Martha's car, not just bounce off or break the back window lol. But meh.
And what to make of next week's episode... was that a considerably older Captain Jack?