I thought it was okay to good. The best part was that she really did deliver that "he built it" line extremely well. It's hard to get that timing right, and she nailed that.
But it wasn't really very specific a portrait of her husband. Kind of a lot of generalities, and asking us to take a lot of things on faith.
It oddly echoed a lot of the speeches so far tonight: not really very much about Mitt Romney! Santorum, Walker, McDonnell...they all sorta mentioned him, but that was about it. And now even his wife didn't really give very much of a portrait of him--no little stories about the time Tagg had pneumonia, that kind of thing.
She was, to give her some credit, the first speaker of the night who tried to reach out to non-conservative voters. She wasn't bad by any means, but it won't be remembered in two or four years, even if he does win.