Apple has released a public beta of OS X 10.10.3 featuring the new Photos app.
First impressions of the new app indicate that it is a vast improvement over iPhoto. All registered public beta test members should be able to download OS X Yosemite through the Mac App Store.
The build is number 14D87p. That’s the same build that was seeded to developers on February 23rd.
more at Apple beta program