Having all those images at hand might make you nervous about ever finding anything again, but luckily, Apple is adding a smart-search feature and a Favorites button. The search field will initially prompt you with a collection of nearby photos, images taken at the same time last year (for the nostalgia factor), and all-time favorites; but you'll also be able to search by date or time, location, or album name.
There are new editing features for images, too: Download an image to your device, and you'll be able to use a bevy of iPhoto-inspired features to crop, straighten, remove red eye, adjust lighting and contrast, and more. All of those edits sync across your devices, so that the fixed image appears in your library immediately. They're also non-destructive: if you decide you preferred your image unfiltered, you'll be able to revert it.
On top of that, OS X's Extensions for developers means that your favorite third-party apps could provide filters and adjustments that you could use from within the Photos app.
What does that mean for iPhoto? It's a good question. For many users, it might replace iPhoto entirely. It remains to be seen if Apple will reposition or refocus iPhoto for a different audience, or if iPhoto will soon join Dashboard on the list of Mac technologies we shouldn't get too attached to.
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