Horodruin's interface is simple, but that's all it needs to be. You add sources (folders to be synchronized), analyze them, then use the sync function. If you know data in a particular folder has changes, you simply use the invalidate function and then analyze it again. The program doesn't sync open files; also, you have to re-analyze folders each time the program runs.
I like Horodruin, because it doesn't try to do too much and what it does, it does well. The English translation of the help file was a bit weak, and I didn't like the download of the required Delphi Control Library being referred to as an "extra" installation task (the program won't run without it), but all in all it's simple and effective. Other features include the ability to load and save sets of folders to synchronize, as well as inclusion and exclusion filters.Caveat: Data will sometimes be overwritten when syncing (never versions of files replace old ones) so make sure you know what you're doing and that your clocks are always set correctly on all your machines so the file modification dates are accurate. Otherwise, you can lose data.
--Jon L. Jacobi