Year over year, analysts and journalists, myself included, have been predicting that "This is the year of NAC" and "There are too many NAC vendors and the market is going to shrink." Neither prediction has really come true.
There are, perhaps, many reasons why the first prediction hasn't come to fruition. NAC technology is too immature, too complicated, too costly, doesn't solve the right problem, doesn't solve any problem, too brittle, doesn't have enough integration points, too few standards, no clear leader, no established best practices, too many exceptions, not effective enough, requires yet another agent, does use an agent, requires costly upgrades to existing infrastructure, requires new support products and processes, and so on.
I've been looking at a lot of NAC products lately and the products are in varying degrees of maturity. When pressed about this or that missing feature, vendors invariably say the feature is either in the pipeline, doublespeak for "We had to add it to win a customer" or vendors say they will add it when there is customer demand. Usually the latter statement is said in the context of a sigh and further explanation that while the feature may be useful, their developers have to focus on features based on demand, meaning paying customers or prospects.
Given the competitiveness of the high-tech industry and the uncertainty in a new technology market, startups need to be brutal in prioritizing projects. I understand the vendor's point, but it's a tough way to make a product.