NServiceBus makes it easy to monitor the performance of any endpoint that has the performance counters enabled, which includes any endpoint installed with the production profile. After having installed NServiceBus and a service with counters enabled, you will find these counters in the NServiceBus category in the Windows Performance Monitor:
Number of message failures per second
Number of messages pulled from the input queue per second
Number of messages successfully processed per second
Critical time
SLA Violation Countdown
The last two are especially interesting. Critical time is the age of the oldest message in the queue, or in other words, the length of the queue's backlog in seconds. This is important because it is how business stakeholders will judge the capability of your system. In a messaging system, your business stakeholders probably don't care what your overall throughput is; what they really care about is whether their work gets done within a length of time...