Here's a link to the actual presentation https://web.archive.org/web/20100817162301/http://dl-web.dro...
I mean, I guess I'm glad they didn't pull a Google and break it in new and exciting ways every 6 months, but really, it should have been changed back a week after they screwed it up.
Big congrats to the Dropbox team, though -- I use their product personally because it Just Works. Interviewed there back in 2011 when the office was (next to?) the old Fry's in Palo Alto.
The % used is seen when you click on the settings. I think because, honestly, they're trying to abstract the idea that you need to do that (the average user just cares that it works not the %).
Get where you're coming from tho - it's not the most clear or clean UI.