As regards the mechanical properties, the top bracket is. However, can be by myself with the current firmware (have a Vodafone branded Galaxy S Gingerbread 2.3.3) does not accept the audio output in operation - only produces strange noises.
Various forums suggest that this is due to a software bug that will be fixed in 2.3.4 alleged. Just how long it will take over until the next firmware update comes? When a friend who has a so-called Custom ROM, it works.