have you ever seen the web interface?

Yes, but I honestly believe it suffers neglect and a lot can be done to improve it. I have never seen a posting for a UI Designer hence wondering.

Also the major USP is that Dropbox behaves just like a folder on the OS and not a seperate entity.

I was just pointing out that there definitely is a UX piece and plenty of room for designer contributions.

Not to mention the installers and the rarely-used menus and preference windows. Just because you don't see them very often doesn't mean they wouldn't benefit from thoughtful design.