I'm learning about Windows Server 2008 R2's NAP features. I understand what network access control (NAC) is and what role NAP plays in that, but I would like to know what limitations and problems it has, that people wish they knew before they rolled it out.

Secondly, I'd like to know if anyone has had success rolling it out in a mid-size (multi-city corporate network with around 15 servers, 200 desktops) environment with most (99%) Windows XP SP3 and newer Windows clients (Vista, and Win7). Did it work with your anti-virus? (I'm guessing NAP works well with the big name anti-virus products, but we're using Trend micro.). Let's assume that the servers are all Windows Server 2008 R2. Our VPNs are cisco stuff, and have their own NAC features.

Has NAP actually benefitted your organization, and was it wise to roll it out, or is it yet another in the long list of things that Windows Server 2008 R2 does, but that if you do move your servers up to it, you're probably not going to want to use.

In what particular ways might the built-in NAP solution be the best one, and in what particular ways might no solution at all (the status quo pre-NAP) or a third-party endpoint security or NAC solution be considered a better fit?

I found an article where a panel of security experts in 2007 say NAC is maybe "not worth it". Are things better now in 2010 with Win Server 2008 R2?