As a business we moved to Google Apps a little over a year ago and we haven't looked back. It is almost perfect for a business like ours and as we have now moved the website to Google Sites we can look to save some more money by removing our web space with our service provider.
All of my contacts, emails and calendar entries sit within Google Apps and the iPhone, iPad and MacBook simply sync to these. I certainly have my head in the cloud.
You may notice an Apple theme to the technology. The iPhone has been owned for a long time, the iPad for about a year and the MacBook is a new addition. It is my first Apple computer and I am delighted. It does become a little confusing though. I now have an iCloud account, and to sync documents in Pages and Numbers it happens through that. So now I have my head in 2 Clouds. In fact, I have my head in 3 if you include Amazon for my reading. I also rely on Facebook a lot for personal communication with my friends.
I am trying to work out where this will go. For now it is working, but I already see that different companies are vying for your attention and commitment. It is very easy to be faithful to Apple, for example, and the reality is that if we could use our own domain with the @me.com email address then a move in that direction would be a strong possibility.
In a few years' time the Cloud may well be on a par with our Utility suppliers as we look for the best deal.