Sync in a Blink is a great app for any iPhone user who likes to keep their Gmail contacts as their primary address book. What this app does is it allows you to either sync all your Gmail contacts over to your iPhone or sync all your iPhone contacts over to your Gmail. The process erases whichever one you are syncing to, so make sure that you've selected the right option.
Every time you make a successful sync with this app, you're given a backup log file that you can easily email over to a computer and sync with one of many different mail clients. There's also a log to show you any of the difficulties that the app has had when it comes to syncing up. This is a great way to get your contacts as a saved file, but using it how it is intended isn't very helpful.
Once you set the way you're going to transfer your contacts, all you have to do is press the sync button. It doesn't take that long to complete the transfer either and once it's completed you can confirm the number of contacts synced and other information very easily.
This app is scary. No matter what you do, you're going to lose some contacts or wind up with random contacts on your iPhone unless you create a new Gmail account. GTalk has become fairly popular and few people actually fill out all their information on it, so syncing to the iPHone could leave you with a ton of contacts that are just email addresses. If it had a merge feature, this would be much better.