I guess I need to know more about what you want to monitor. We use nagios (host/service up/down notification), ganglia (host metrics like ram/disk/etc), and MRTG for bandwidth etc, and rsyslog with tenshi for log alerting. If you are a sysadmin then you probably want nagios. I would be suspect of new shiny things, nagios is rock solid and is used as an industry standard for monitoring in many open source shops (think universities, HPC clusers, etc).

p.s. I run a sysadmin screencast site @ sysadmincasts.com. I'll try and do a nagios episode in the next couple weeks.