I found it odd that they didn't have Catelyn observe out loud that the song was "The Rains of Castamere." Sure, Cersei talked about the significance of the song in a previous episode, but most viewers (myself included) aren't going to recognize the song just by how it sounds. It would have been as simple as Cat mumbling the title quietly to herself, or asking Roose Bolton what he thought about it. If I hadn't read the books I'm pretty sure I would have missed the significance.
It was also too bad they couldn't have done the thing with the big tent outside being lit on fire and dropped on the soldiers. Probably it would have eaten through too much of their budget.
But hey, pretty good for the most part. Now we're past the biggest spoiler of the series.