Using Dropbox is most convenient, and based on comments I've seen on HN, no other client comes close to Dropbox for simplicity, stability, low CPU usage, etc. However, our files can certainly be made visible to anyone working at Dropbox. Same with Google Drive, iCloud, SkyDrive, and Box.com.
So, currently, I'm using a private folder inside Dropbox and encrypting it with EncFS. This is not completely secure either, but the bigger problems that I have with this solution is that EncFS or FUSE sometimes fail (especially if I'm trying to copy/paste multiple files) and sometimes the files become corrupted. I can't take that kind of a risk with my most important files.
So, I'm back to square one. What do HNers use for this kind of a need? I've tried Bittorrent Sync but I can't trust that company. I can try using Truecrypt or VeraCrypt which won't be as convenient as EncFS. Or, I can use a client-side encryption solution. Are there any which are as good as Dropbox? What are your opinions on SpiderOak, git-annex, syncthing, sparkleshare, syncplicity, aerofs? Anything else?