>According to this guy http://ryanfarley.com/blog/archive/2004/07/13/879.aspx it's not a good idea to write to App.Config:
>
>Warning: As a rule of thumb, it is not good to write back to the config file. The framework does not include this ability for a reason. If you want your application's users to not require administrative rights then it is always a better idea to store settings in the user's documents & settings directory or in the registry if needed. That said, this won't break anything and does come in handy for utility applications etc.
>
>
>1. Why not? Isn't the point of App.config to save app settings?
>2. If not, then where's the best place to save user settings?
>
>Thanks

Check 3rd video from http://www.pluralsight.com/main/olt/Course.aspx?n=dotnet-csharp-tutorial - it talks about saving application and user settings.

This particular video is free (I watched this course and it was a nice refresher).