Yep, I use both because each is well-suited to different things.
For a small number of critical files and documents I absolutely want a remote copy of I have Dropbox (this is also where Dropbox's versioning comes in handy), while for all my large folders with stuff that's non-critical or already remotely stored I have BTSync, as well as for temporary and ad-hoc sharing.
For a small number of critical files and documents I absolutely want a remote copy of I have Dropbox (this is also where Dropbox's versioning comes in handy), while for all my large folders with stuff that's non-critical or already remotely stored I have BTSync, as well as for temporary and ad-hoc sharing.