Diagnostic, performance and debugging tools are very cool.  The more tools available, the easier it tends to be to find and fix application issues.  With Visual Studio 2005, several handy tools were added.  I use the Remote Registry Editor and Remote File Viewer just about every day.  Version 2 of the .NET Compact Framework added diagnostic logs (enabled via the device registry) to help identify application problems in places where it was very difficult, or not possible to find them with other tools. 

One difficulty with using the diagnostic logs is setting the registry options.  Modifying the registry can be intimidating and, if done incorrectly, a risky proposition.  Readers familiar with my writings on using the diagnostic logs will recall that every time I mention the Remote Registry Editor, I include a warning to use the tool with great care. 
Read more here.