I have brewed a few of their kits and have purchased ingredients from them for other recipes many times. The kits were pretty good I felt (Bavarian Hefe, Czech Pils, English IPA) and the extract seemed to be fresh.
My only suggestion is to ignore the instructions that come with the kit, especially if you are using specialty grains. I follow the methods laid out in the Palmer book (steep at 165 or so for a 20 mins - half hour) rather than doing what NB says which is to remove the specialty grains when the water starts to boil. The latter is not a good method for a number of reasons (tannin extraction, different stoves will boil water at different speeds) Other than that I think the hopping schedules they provide are accurate.
As as aside, I think customer service at NB is great. I once had a yeast pack that didn't activate and an auto-syphon that broke in shipping and they sent out replacements immediately. They can be a little pricey for hops, which is why I bought some cascades in bulk from a hop farm in the late fall.