Announced last night on the public forums, the latest beta of Dropbox 1.5 for Mac brings a completely redesigned popup menu, support for Mountain Lion's Notification Center, a new installer, and better performance.
Sporting a new modern look, the redesigned popup menu is reminiscent of "popovers" that have become extremely popular among iOS developers. The new menu takes a more visual approach at displaying changes in your Dropbox, with icons for added or deleted files (that you can click to quickly go to Dropbox), a play/pause button for sync, and a large "Open Dropbox folder" to launch a Finder window at the "root" of your Dropbox.
This new popup combines all the functionality from the older tray menu with a new view of your Dropbox's event stream, letting you see your (or other people's) latest changes. In addition, you can use the events to easily view, share, or restore files.
Alongside the new appearance of Dropbox in the menubar, the team also says version 1.5 will bring full Notification Center support and a new, simpler installer for Mac users. The new installer works as advertised: you can simply double-click the icon for Dropbox to "update" itself to a new version. Unfortunately, while enabled in Notification Center, I haven't been able to test the new notifications on the desktop, as I assume the functionality isn't quite ready yet in this beta.
Personally, I think what Dropbox is showing in this experimental build is very promising. The popup menu was in need of a serious upgrade, and I'm looking forward to seeing how it will evolve throughout the next betas.
To download the latest Dropbox experimental build (and send feedback to the developers), you can head over the Dropbox forums.