Been using Dropbox forever, got in on the Android beta the first night. This truly makes me realize how game changing this service is-now, without hacks or anything, I can have access to my whole filesystem from anywhere.
The app itself is excellent-it is simple, makes sense, and allows you to do what you expect-view and edit files, from anywhere, and in-sync in all locations. It also lets you access media stored on the DB, and you can upload right to it.