Configuration for iPhone and Windows Mobile devices is easily performed via their respective ActiveSync and Exchange configuration features, but there are a couple of caveats you should know about first. For starters, setting up your phone to sync up with Google's servers will wipe out any existing contacts and calendars from your device and after syncing Google's contact manager becomes the one place where all contacts are stored. Also, the service only currently supports up to five user calendars and there are already a few known issues when synchronizing the calendar.
Google Sync has been available for BlackBerry users since some time last year and apparently it also works on other SyncML enabled devices such as Nokia S60 and Sony Ericsson smartphones. It is currently in beta and right now it notably lacks support for push email, but if you give it a try be sure to share your thoughts in the comments.