I'm looking at CloudPull to back up my Google data. Yes, you should back up Google data. No, I don't think my local hard drive is more reliable than a Google data center, but hardware failure is the least of my concerns. Consider what would happen if you lost access to your Google account. Um hmmm... Now see how many ways you can think of which would cause that to happen. Still think you don't need a backup?
Oh, and when I search my files on my Mac, I expect to find all of my files -- not all of my files except my Google Docs.
CloudPull has a genius trial version. You can back up one Google account (that's all I want) and you can only run the app as a U.I. app (which I don't want). I can thoroughly confirm that the app meets my needs and I can take as long as I want. But if I continue to use it, I'll definitely register it because I want backup to run invisibly in the background.
Important things to know about CloudPull:
More as I get experience with it...