Nate Silver doesn't forecast House races because there isn't enough good polling data. He does predict Senate races; he was 31 for 33 in 2012. He predicted that Republicans would win in North Dakota (a 92% probability) and Montana (66% probability). Democrats won both races.

Here is the link to his 2012 predictions:

http://fivethirtyeight.blogs.nytimes.com/fivethirtyeights-20...;

Just click on the Senate forecast.