As an otherwise-happy Dropbox customer, it does concern me somewhat that there has been very little innovation in the core product for several years. They seem focused on building a halo of lock-in services instead.
I don't know, their core product is so solid. It's one of those things I can install and never think about again, it just works. Maybe there's no need to innovate there?
There's need for innovation because Google/MS/Apple and such are integrating cloud-sync right into the operating system (and its only a matter of time before their sync tech is good enough or better than DB's sync tech).