I've been using Sync Pro for several months now. Prior to v6.2, it was pretty buggy. It didn't crash much, but had lots of problems with deciding whether a file needed backing up. (Have a look at the Synk forums at the developers site for an accurate snapshot of the problems people are having with the software.) v6.2 however is a very solid product. No crashes and handles my backup needs without errors. The best feature of Synk is that it has a daemon that can do all the backup chores without the main app running. Very convenient. The only issues I have now is that the new GUI in v6.2 was initially a bit confusing, and Synk doesn't gracefully deal with scheduled backup operations to network drives when I disconnect my computer (laptop) from the network for travel. It doesn't crash, but scheduled operations don't automatically resume when reconnecting to the network. I've been told that the authors are working on this though.