What Do You Use for SNMP Monitoring?

linuxi386 wonders: "My company is in the process of implementing a global frame relay system. The network will cover 20+ states, and several European and Asian countries and Australia. It will have a 5 point full mesh fail-over with each coast/country having about 20 ppp links about 30 servers mixed between linux and windows plus a 2003 domain controller at each site. I have been looking for a really decent cheap web based monitoring application to maintain the entire system. So far I have looked at Solarwind's Orion and Adventnet's Opmanager. I like the look of Orion, but while I prefer the feature base of Opmanager, I cannot stand its pricing model or the XP playskool style theme it uses. I am trying to avoid writing my own system to manage this if at all possible. What would you folks recommend and why?"