Here's the first Public Beta version OS X Yosemite 10.10 beta 1 Build 14A299l. You can grab this directly if you previously signup on Apple Dev beta program. As you can see here, the build number is different with previous developer preview.
There are a few known issues with this build, that participants should be aware of.
Safari may hang when playing certain Netflix content.
iPhoto 9.5.1 and Aperture 3.5.1 are required on OS X Yosemite. Update to these versions from the Mac App Store.
When entering edit mode in iPhoto, a black screen may be displayed instead of the selected photo.
Photo Stream and iCloud Photo Sharing may not function properly when both iPhoto and Aperture are installed.
The shared purchase history page on the Mac App Store is disabled for Family Sharing accounts.
iCloud Drive may appear empty in the Finder after first time setup. Restart to resolve this problem.
AirDrop may not show nearby Macs.
Sending files to another Mac using AirDrop may not work.