I find Zabbix to be a fairly decent monitoring and measuring system, because you can use it for both snmp and zabbix agent based tests. It's quite easy to add new measurements. The triggers/alerts work well too. It's not as flashy as the latest tools but if set up right it's fairly easy to get to the information you want.
If I wanted to measure network latency then smokeping works well. Two words of warning: firstly the smokeping agents can go bad and start eating all your memory! Secondly, the configuration is quite brittle, and (I don't know if they fixed it) but running the master in debug can stop configuration changes propagating.
