We do not monitor the access layer, with one exception, the uplinks to the distribution layer.
We also do not monitor unicast or multicast routes. However we have been discussing our options for unicast monitoring.
We have established baselines for all nodes and have created exception rules for nodes like SQL and Linux servers. Nodes with exceptions are grouped by type for reporting and alerting purposes. Makes it much easier for both.
We do monitor link saturation but on specific links not on all. We also have a couple links that we monitor and alert on when the link utilization is NOT above 15% for 5mins during certain times of the day. We perform 1000s of FTP transfers several times a day. If the outgoing links are not being utilized during the transfers, something is not right.