I've been fully committed to Dropbox for over two years and now keep all my current data on the service. The great strength of Dropbox, though, has always been its greatest weakness. All data is stored locally, synchronised with the Dropbox cloud and then re-sychronised with an identical data folder on all your computers (even iPhone and iPad). The result is that you have exactly the same data everywhere, plus the peace of mind of on-line backup.
Up to now, though, the amount of storage you've committed to Dropbox is limited by the capacity of the smallest computer in your stable. It has been impossible to put 100GB into Dropbox when you have only 64GB or 128GB storage on one of your laptops (as is the case, for instance, with the new 11-in MacBook Air). This has been the greatest weakness of Dropbox and limited the benefits for many users.
Now Dropbox has been updated (version 1.0, strangely) to include much-needed selective sync where you can specify the folders to be synced with individual machines. For instance, you probably don't need your photo library or, even, your full music or video library to be synced to a road-warrier machine such as the Air. With the latest Dropbox you simply tick the folders you'd like to appear on each of your computers. I've been trying out the beta version for a couple of months – ever since I bought my 11-in Air, in fact – and the new system has worked faultlessly.
Having tried other cloud backup solutions, I am convinced that Dropbox is by far the most user friendly and reliable. You just install it and forget about it. All my spreadsheets, frequently used documents and databases (such as my account system data and the 1Password file) are on there and are accessible from any of my computers. Dropbox is also increasingly used by iOS applications for desktop sync. For instance, the excellent Elements text editor for iPhone (and iPad) stores its data in Dropbox so you have instant access to all notes when using any of your Macs. There are dozens of similar examples and Dropbox is rapidly becoming the sync-engine of choice for iOS developers.
In the past two years I've introduced Dropbox to many friends and colleagues – including many who are technophobes and don't want to know the details. They now accept that all their data is available on any of their laptops, desktops or iPhones and they don't question how or why. It's just there and it works. That's the beauty of Dropbox.
Most of these friends are managing with the free Dropbox service which handles up to 2GB of data. If you want more – up to a maximum of 100GB – you have to pay, but it's well worth it for the convenience and peace of mind. As I've said before, Dropbox is what Mobile Me ought to have been.