On the functionality end of things I think dropbox should be stop new feature development until heavy UX is done with large unbiased test groups. The application is simple and it works pretty well but recently I've noticed different barriers to use, notifications that I'd prefer not to see just getting in the way. It's a result of Zawinski's law, it's happening to gmail where they think adding more bells and whistles is needed but it's not, in many case user experience declines, for example playing a youtube clip now blacks out the rest of your gmail page while you watch it. Application developers need to learn that less is more.