I've done the Usability Week courses with NNg and found them amazing. I would disagree with Hilary in they do run courses and workshop intensives a lot to take in if you are a beginner.
I did do the Usability Week interaction intensive and got so much out of it.My learning took an exponential leap and continues to be a grounding in interaction design principles from Tufte to Deyfuss to Fitz.
The teaching weren't just about websites and the digital world which I really appreciated.And I had the privilege to spend a few days with Bruce 'Tog' who had a great delivery of stories that combined with the leaning content I found invaluable.
Hope it helps weigh up the options. I have heard though, if you are a HCI type of person then the courses are probably not for you.a self assessment thing I would say.