Sync programs are a dime a dozen. However, tightly written, easy-to-use, and nearly feature-complete sync programs such as @Max SyncUp are not. SyncUp walks that fine line between power and ease of use very well, and succeeds largely because it puts options within easy reach, yet keeps them simple and uses as little technical jargon as possible.

SyncUp ($25, 30-day free trial) has nearly every feature you could ask for: backup, file filters, scheduling, and both two-way and one-way synchronization, as well as support for domain users, email notifications, FTP servers, networks, and very granular scheduling. However, a possible weak point is the lack of online destinations. Google Drive is supported, but nothing else. If you want to back up more than the 5GB that Google Drive allows, to say Amazon S3, you'll need to look elsewhere.

While SyncUp doesn't support revisioning as such, it will keep multiple older versions of your files. It also syncs using plain file copying, to zip archives, or to its own proprietary encrypted archives. The program spawns its own service as well that allows it to perform scheduled operations whether you're logged in or not. Nice.

@Max SyncUp is well-executed. If you use S3 or any other non-Google online backup or storage service, it may not be for you, but otherwise it should be on your shortlist of pay sync programs if freebies such as FreeFileSync won't do.

Note: The Download button on the Product Information page will download the software to your system.