There is much to be desired with Alert Management.
Once an alert is created, it is hard to see what it is actually set to measure. There is no indication of what report the alert is even attached to.
It seems like you can't set up an alert for a metric on a classified value. For instance, if you have a page type classification and want to set an alert for when a metric surpasses a threshold just for that classification, it seems like you can't do this. Or if you can, it doesn't get represented properly in the management screen.
You cannot create alerts on Calculated Metrics.
You cannot create alerts with segments applied to a report suite.