The actual plot was a good one. The Time Lords find an escape route, only it turns out that this is really bad news, because they're eeeevil. I'd happily watch that plot. Having it tie into The Master's brain-drums works for me too.
What didn't work for me was then managing to waste two hours of screen time to the point where this plot was somehow squashed into fifteen minutes of plot, we have to have the evilness of Gallifrey explained to us (SHOW! DON'T TELL!) so quickly that at least two people I was with managed to miss it, and instead spend an episode and a half on The Master prancing around, two green aliens that don't actually add anything to the plot, Star Wars rip-off scenes and The Doctor falling through glass ceilings for no reason.