I have used Solarwinds NPM since it was Orion. I have found that with a little effort, the latest iteration is an extremely powerful tool. I leaves Openview in the dust. The reports can be customized with either a simple interface with a complex SQL query. Alerting is superb. You can even set the alerts so that you will not get flooded when key components fail (as in WAN links) The licencing is not actually per node, but three levels of maximun and an unlimited. Either way, the pricing is extremely reasonable and the anual is for supporty and upgrades. The people at Solarwinds have always been very responsive.