The Tolly Group released a report comparing the Network Access Control of Forescout, Bradford Networks, Cisco Systems and Juniper. Disclaimer: Tolly performs paid research, and in this case is paid by Forescout. Nevertheless, they do a good job comparing product. You should just take it with a grain of salt.
I’ve used Forescout for about four years. I think there is an ease of deployment that is unmatched. There is also a great flexibility in the type of rules you can apply.