Anyone Using any sort of Network Access Control (NAC)?

[StarTrek4U]

We're evaluating some new technologies for deployment into our network over the next few years and I was wondering if anyone here has deployed any type of NAC solution on their network and what their experiences were. I know that most of the major players have some sort of solution usually with a partner vendor (cisco and MS for example). I'm curious to hear who/what you use and how it works.

Thanks in advance.