Dropbox is a new file-synching service, still in beta testing, that has some welcome features despite its simplicity.

Like other synchronisers, Dropbox requires that you download and install software; but un­like the others, it has almost no user interface. All it has is a tray icon that you click to see a pop-up window with one command for launching the Web site and another for opening an Explorer window to the Dropbox folder installed in your Documents folder.

The majority of your file-synching and -sharing happens through the folder. You drag files and folders there to have Dropbox automatically upload them to the servers (beta testers get 2GB of free storage; in the future only 1GB will be free).

You can also share files by transferring them to and from the Dropbox folder.

If you upload a file that isn't in the Dropbox folder directly to the Dropbox site, a copy will appear — you guessed it — in your local Dropbox folder.

Although having a single place to drop your files for synching can be convenient, Dropbox makes it mandatory, not an option like SugarSync's Magic Briefcase folder. Being required to keep all your shared, backed-up, and synced files in a single folder is an annoyance that Dropbox's makers promise to correct in a future version.

Despite that flaw, Dropbox is an extremely simple program that offers some valuable features, including maintaining copies of deleted files in the Web interface (click Show Deleted Files to see them), and providing access to past versions of edited files.

As with every other synch program we've tested, sharing involves sending an invitation to collaborators — but Dropbox doesn't make inviting multiple people easy.

Invitees are asked to install Dropbox, which causes the shared folder to be copied and synced with their Dropbox folder. If your invitees don't want to install the software, they can still access files through the online file manager as long as they log in and know the URL.

Dropbox's online file tool is even more limited than that of other products. To see thumbnails, for example, you must drag pictures to the Photos folder within the Dropbox folder, since that's the only one that has a thumbnail view online.

The pricing for Dropbox is not set yet, but the cost is expected to vary with the amount of server space you require.