RIDGES  I've been using SP for four years and it has been truly invaluable, keeping my documents folder on a desktop and laptop perfectly synched. It has not corrupted a file a single time to my knowledge. The bootable backups boot perfectly. I just updated to 5.1.3, but the prior version, 5.0.3x never crashed.

The setup is a little awkward, but not a big deal and you only do it initially - running the synchs is easy. Backups are critical to your happiness, so spend a little time to set things up right for yourself. Would I want a slick "metal" interface - noooo way. I want the programmer guy spending his time on data integrity and reliability. Do I want a creative kind of guy coding backup software? No, I want an anal-retentive, list making, accountant-type of unimaginative nerd.

A complaint about the backups is incrementals are done using a hierarchy of "archives". I would prefer to simply set a back date and browse files directly. It is, however, easy to find an earlier version by browsing the archive as necessary.

Bottom line is that for absolutely critical data integrity I have not had a problem for four years and for that I will put up with anything and the $99 is not unreasonable compared to all the buggy junk out there for cheaper. If you have a crashed computer you will pay anything to get your data back. Do not compromise on your backup strategy in order to save a few bucks.

#1 Gripe is license agreement as others have pointed out, although he's changed it so you can use it on two computers, but with restrictions on the second. To restrict use on the other computer is ridiculous - the software's purpose is to synchronize two computers, so the software has to be available on both computers - simple. Note to Qdea: please just remove the silly restriction on the second computer. How many users will actually pay you twice? Answer: the nicest, most ethical and well-meaning people on Earth. They deserve a break please give it to them.  
(Version 5.1.3)