We have an entire support division that does SNMP management
We also use WMI, ICMP and whatever else we can to garner data.
Before we wrote our own we have used them all from Cacti, Nagios, opennms to Orion
Knowing how to set them up is 1/2 the battle
SNMP is a complicated protocol to undertand the first time
once you know it, it isnt' that hard
companies frequently spend months setting up their solutions
We have done it before and can either help you evaluate a system that is right for you or set one up for your company. We also have our own which you are welcome to try out and see if it wil lgive you the results you need.