I hate Dropbox. I would never give any of my files to Google. I think “cloud” is marketing bullshit for “Internet”. The only syncing I use is PhotoStream on my Apple devices to synchronise photographs. That sucks as well, but who cares if a photo doesn’t show up on some device. Apple’s MusicMatch, the “cloud” music service, blows.
For sharing files, I upload them to my site and pass a URL to the recipient by IM/chat or email.
—ravi