They released a delta API recently. It's a bit of a pain to perform this task as you can't differentiate between a new file and a renamed file or a file that's been moved from one location to another.

In all cases you get a delete (if the file isn't new) and then a new file event.

I implemented it, and it kinda sucks for this sort of thing. The purpose seems to maintain local state to mirror the state on Dropbox. Not terribly interested in that...I just want to subscribe to specific events (webhooks, anyone?).

This was their solution to the frequently requested webhooks. It falls short. Way short.