I have tried out owncloud, sync and others free self hosted syncy things. All of them have freaked out the CPUs on first sync, struggled with many files and some can't do *nix file names.
They all have done the syncs brilliantly with about 100 or so random files to and from one M$ and two Linux system and android phone.
Depending on what you want the GUI is OK and easy to set up, each to their own, so coming from x to y takes some getting used to, but hey that is life.
But when I did a full scale test, 65Gb music, 100Gb photos and 40Gb random files/document I have collected over the years. Between a full system, to a new empty backup drive and to a backup drive with a carbon copy(rsync).
They all failed. Nearly all of them spends a day or so scanning my files, starts, figures out that its a while since they checked for updated or new files, scans for many hours with CPU red hot, lappy reboots, program eats memory and gives the CPU another hot flush, while it scans my files and so on. Gave up using/trying the program as I would like to be able to use my lappy while this went on. Heck one even started to rename my files. Another fecked up the time stamp on the files too.
So now I use rsync, when I remember, need to set up a cron, as that don't freak out my CPU. Which I don't understand as one of these says they are just an easy web GUI for rsync, but I could have a BBQ on my lappy when it ran.
Dropbox never has any problem, though biggest test is about 7Gb photos, it just works.
Will test out decline too.