I switched to Syncthing a while back and haven't looked back. It's self-hosted, so there are no storage limits, and if you care to put in the work (setup is a tad more complex), it's also pretty easy to hook it up to a cloud server, which nets you an off-site backup.
Syncthing doesn't quite have the "Just Works" factor that Dropbox's offering has, but I don't need that; the ability to synchronize several terrabytes of my personal archives (I have a lot of data) was more than worth the effort.