Question : C#, general purpose logging

Your opinion is most welcome.
Before we begin to develop softare we are looking for a general purpose logging approach.  I’m just wondering what others are using and why?
To date, we have considered these.
Performance is not a strong consideration.

•Trace Listener : http://msdn.microsoft.com/en-us/library/system.diagnostics.tracelistener.aspx
•System.IO.Log : http://msdn.microsoft.com/en-us/library/system.io.log.aspx
•TraceSwitch : http://msdn.microsoft.com/en-us/library/system.diagnostics.traceswitch.aspx
• Logging Application Block which can be found at : http://msdn.microsoft.com/en-us/library/ff647183.aspx
• Log4net which can be found at : http://logging.apache.org/log4net/

Answer : C#, general purpose logging

We use two seperate methods for logging, which is Log4Net (general application logging, and used for some services).  And of course Event Viewer, which is a simple way to implement it (Log4Net also has the capability to log to EV).