I'm not someone who likes promoting products that is not Open Source or at least free, but since using SpanningSync - costing a mere $25,00 a year - I'm really enthousiastic about the product. It just works and is invisibe ...
My scenario is somewhat different than that of most other iPhone users. I own 2 SIM cards, 1 Dutch with unlimited data traffic and 1 Italian prepaid without 3G options. As i currently live in Italy, using the Dutch SIM to access the internet would be costly, so I'm restricted to using WIFI whenever and wherever i can. Not being constantly online with my iPhone makes syncing the iPhone with Google Apps hard. I've tried the free NuevaSync, but i've noticed that i forget syncing regularly.
Using SpanningSync is transparent. It installs on OSX, syncs iCal with Google Calendar and Address Book with your Google contacts so that i can sync with my iPhone via iTunes. This way, when syncing my podcasts, music etc. i automatically sync my iPhones calendar and address book to 2-way with Google Apps. Having GMail configured on the iPhone as well, makes working with Google Apps a seemless experience.
As a bonus-tip that will further improve your Google Apps experience on OSX: Install Google Notifier for Mac and Reader Notifier and you're good to go!
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