syncronizing on a Mac is not an easy issue. I tried rsync, then unison and now I come back to rsync and your GUI. If I may suggest: For me it would be of utmost importance (since I do not trust myself telling arRsync to do the right thing) that I would see what rsync intends to do, then choose if I like rsync to do it before it does it.
Too complicated? Have a look at the GUI of unison once it found differences. It beautifully shows which file is updated where, let's you choose the "direction" of the update or to skip the file at all. Would be great to have a good sync tool !!