Macworld:

Providing many of the features found in its mobile sibling, the Yosemite-only Photos for OS X offers an interface less cluttered than iPhoto, improved navigation, simpler yet more powerful editing tools, the ability to sync all your images to iCloud (though it doesn’t require you to), and new options for creating books, cards, slideshows, calendars, and prints. I’ve had the opportunity to take an early look at Photos, and this is what I’ve found.

This is the developer preview but, in my experience, it’s pretty stable with few true glitches or bugs. Keep in mind, this is not (yet at least) a professional Aperture or Lightroom level app. But, that being said, it’s still pretty good.