Google+ Photos has always been one of the site's most worthwhile features. Facebook has made up some of the gap in the meantime, introducing larger thumbnails, better album layouts and so on. But Google+ is still putting a lot of emphasis on photos.
In the latest update, Google has made it possible to view photos in an album in a slideshow. Nothing remarkable about that necessarily, but it's been one of the most requested features.
But Google is not done, along with the new slideshow option, Google is making it possible to download full albums. Visit any album, click the More button and you'll notice the "Download album" option. Google+ will then provide an archive, a .zip file, with all of the photos in the album.
If you don't want people downloading your albums, and would have them go to the trouble of downloading photos one by one, you can disable the feature in the Settings page, just search for "Allow viewers to download my photos." Obviously, this only disables the "Download" link for photos or albums.
Anyone will be able to manually save any photo you share with them and will be able to download entire albums if they go through the photos one by one or by using automated tools. If you really have a reason for not wanting people to be able to download your photos, outside of hubris, don't put them online in the first place.
The new features are nice, especially the download option, though Picasa users know how limited the Google+ Photos option is compared to Picasa Web Albums + the Picasa desktop client. The nice part is that you can still use Picasa, all of the photos from Google+ will be there.
Via: Download Google+ Photo Albums and Fullscreen Slideshows Now Available