File Sync Services and Software for Mac OSX

This thread start and summary from UCSC Mailing List might prove useful to others. 
 On Friday 20 November 2009 Harry Mangalam wrote: 
 Is there a good, free, OSS , or commercial file synchronizer for the Mac? Or a verified web app that does the same? 
 A (surprisingly) data-security-conscious client wants to use a USB disk to sync his desktop to his laptop at home and has tried a number of apps that do not work well. 
 He was very keen on the commercial service Sugar-Sync until it started to frag his data and required regular manual cleanups via their tech service. He has since soured on Sugar. 
 Time machine seems to be a versioning app rather than a synchro app. I haven’t used it, but he has and claims that it doesn’t do 2way syncs. 
 He’s tried to use Bombich’s Carbon Copy Cloner, but it does not (and will not) allow ‘remote to local’ sync’ing bc they don’t trust users to avoid overwriting critical boot disk files. 
 I set him up with an crontabbed rsync backup for regular sync’s to a remote server, which he’s quite happy with, but he’s not a CLI geek and has already come close to wiping out his archives by playing with the options, so I’m reluctant to set up such a system for him to do this with naked rsync. 
 I tried Unison for him (this is what it was designed to do) and while the GUI is simple, it works very well and does allow both local 2-way syncing (as to a USB disk) and remotely (via a number of protocols). It also has a native Aqua interface, but there’s no Snow Leper finkable version. 
 Are there any other obvious-to-a-Mac-user choices that I’ve missed? 
 Harry Mangalam – Research Computing, UC Irvine 
 On Sunday, November 22, 2009 Harry Mangalam wrote: 
 Thanks very much to all who replied. There’s no clear winner for Snow Leopard, but I’m leaning towards Unison for the actual sync’ing process that my client requested, as long as I can get it compiled on a 10.6 machine. 
 Here are the answers, compiled into one page. If you have additional info, I’d be happy to add it. 
 http://moo.nac.uci.edu/~hjm/MacOSX_File_Sync_Software.html