This method operates as advertised, but there are two important points to consider before using it:
1. The method conducts changes on the *local* server only. If you include a call to this method in a custom FeatureReceiver and activate it on a multi-server farm, this method will not impact any server other than the server hosting the central admin site (assuming activation is performed via central admin).
2. As stated, the method caller must have local administrator rights on the server. If they do not, the method call will fail and an "Access Denied" will be logged in the server's Application log.
For more information, see
http://sharepointinterface.com/2009/06/06/the-applyapplicationcontenttolocalserver-method-and-why-it-comes-up-short/