There are several reasons to monitor FAST Search Server 2010. This wiki page is meant to document each of the reasons and provide guidance on what to monitor.

What are Some use cases that one should monitor? How should you monitor?
 The recommended solution is to use SCOM 2007 SP1 or R2. Find more details here.

A full list of the performance counters and WMI classes can be found on the TechNet site

The recommended performance counters are listed below: