NTrace
Everyone who writes systems at any reasonable scale needs a high performance logging solution. A number of these exist with varying degrees of functionality and complexity. I have been using NTrace which is a managed wrapper around the windows Event Tracing for Windows (ETW) libraries. ETW is a high performance trace system implemented as a device driver that was first introduced in Windows 2000. There is not a lot of info out there on ETW although it is beginning to gain some traction. I know that it is used internally at Microsoft as a tracing and instrumentation solution in large systems. For a background on ETW see this MSDN article.
NTrace is an elegant wrapper with an easy to use syntax.
EtwTrace.Trace("Item {0} Was not added to the database. Message: {1}", itemId, ex.Message);
The messages are compiled into TMF files which combine the text with the message Ids and data from the ETW system when viewing a trace. Some other awesome things are adjusting the trace level on the fly…a must for high performance applications. ETW supports circular log files which is highly useful. The performance of ETW is ample for even the most demanding applications. It is possible to instrument an application at a very detailed level and with very little performance cost.
Microsoft allows WCF and WPF both to log to ETW. I am moving all my WCF logging into ETW. The Service Trace Viewer can still open the resulting files.
The only downside is the precompiler does not provide a lot of information as to the nature of any errors that you made.