I'm in the same situation with the OS X client. I was using BTSync + Arc to essentially match Dropbox's feature set, but in the past couple of months BTSync seemingly lost its mind with respect to CPU usage. It would routinely hit 100% and would always show up on OS X's "Apps Using Significant Energy" list. I had to shut it down so often that it ultimately wasn't worth it. I switched back to Dropbox and abandoned any sort of privacy once again.

I've currently (slowly) migrating from Dropbox and BTSync to Syncthing. I'd say you might have a glitch in the matrix if BTSync is running that high without any active transfers.

On my (already battery-starved) laptop, it would always suck up 100% CPU for a few minutes on a fresh boot, and then occasionally pop up now and again.

On my (PowerPC!) NAS, it was constantly using lots of CPU and RAM, although I have a feeling plenty of that was caused by swapping to disk (NAS only has 128MB). I love the fact that BTSync have the forethought to provide a PowerPC client for people with outmoded NAS's like mine, just disappointed it was still too heavy to work reliably.

I'm completely switched over to Syncthing/Pulse or whatever they're calling it now. I have no trust for a proprietary "cloud" with my data.

Would love it if Pulse had the option to encrypt the stored data (currently it only encrypts during transmission), so it could be used on untrusted hosts.

Yeah, definitely. It would be a lot easier to have multiple redundant copies of my data if I didn't have to worry about securing each one.

It's one of the main reasons I picked Duplicity for backup.