Since I use three different Macs regularly the importance of having up-to-date data files is more than ever important. If I pick up my MacBook Air and go out for the day I want to be sure that I have the latest version of my MoneyDance accounts data as well as other files I need to work on frequently. The combination of MobileMe and the iDisk is supposed to address that problem. While MobileMe works seamlessly to synchronise primary data (Address Book, iCal, Mail, Safari bookmarks and OmniFocus tasks) across several computers and the iPhone, the same cannot be said for iDisk. The Apple system is perhaps over-ambitious and becomes slow and unreliable. The iDisk, which acts as a mountable drive, has a mind of its own and often disappears and has to be fettled back into life. it is best used as a Cloud backup, but even then is beaten by Carbonite, Backblaze and other similar purpose-built solutions.
If you want reliability and the ability to see and work on data files on a number of computers, the answer is Dropbox. I've written about Dropbox before, but I have now been using it for over six months and have been mightily impressed by the speed, reliability and integrity of the system. Essentially you file your important day-to-day data in a Dropbox folder which can sit on the desktop. Open that folder on any other machine (provided you have the passwords) and a replica of that file is available there. Work on that file anywhere and the latest version is replicated within seconds to all your machines. Unlike with iDisk, you are in full control and you can actually see what is happening.
I run Dropbox as an easy way of synchronising selected files although I also have Carbonite running in the background (on one master computer) and backing up all crucial data. Solutions such as Carbonite are great for the belt-and-braces security of off-site backup of a hard disk or a user folder, but Dropbox is better for precise control of synchronising and monitoring selected individual files. Of course, in addition to the features I've outlined, Dropbox also safeguards your files and provides Cloud access in emergency. The latest versions of your files are already sitting on all your computers as long as they are running and connected to the net.
Another useful feature is to attach your Dropbox to a specially authorised folder on a friend's or colleague's computer. I do the bookkeeping for a physiotherapy clinic in Athens and, of course, I am in another country a lot of the time. So I have arranged for the MoneyDance accounts file on the remote computer to be linked with my Dropbox so I can work on the file wherever I am. Back in Greece, the staff of the clinic can see the latest version of the accounts system when necessary (on a PC, by the way). Of course, sensibly you should avoid the danger of two people trying to work on the same file at the same time, although Dropbox will try to cope with this by storing temporary files. Best not to risk that, though.
There are lots of solutions out there to synchronise files across computers and across platforms. Evernote, for instance, is a wonderful way of storing notes, picture memoranda and data across several computers and the iPhone, and I rely on it constantly. However, the difference with Dropbox is that you can synchronise datafiles from all applications–Word, Pages, Numbers, you name it. All are fully addressable and available for update at any time. More than that, Dropbox keeps incremental backups of your files so, in emergency, you can go to the web interface and look through the history of a particular file.
Dropbox has many more features, such as folder sharing and photo publishing with friends and colleagues and works cross-platform on OS X, Windows and Linux. Eagle-eyed readers will see from the logo that the product is still in beta, but I must say that in six months it has been rock solid and I wouldn't suspected the beta status. As far as I'm concerned, it's ready for mainstream already. It's free, for storage up to 2GB of storage; above that it is $9.99 a month or $99 a year. I am still way under the 2GB with only 118MB in use, but I wouldn't hesitate to pay if I needed the extra storage. Here's a link to the installation page of Dropbox.