Excellent!
In my situation, 99.9% of the computers that are in use on the network are windows machines. I could scan with nmap or languard and which ever one pops up with something other that windows, I can further investigate.

Also, for checking the MAC addresses, I can log into the switch and view the MACs from there; no need to ping/arp. Comparing the MACs to the registered list is what I thought about first, but a test cable/dsl router i have (linksys) has a MAC address matched to some other company.