The Shoebox app has a number of interesting features, such a crop and auto-flatten the images, dating for the photos, geolocation and tagging. The auto-flattening feature automatically spots the edges of the photo and auto-corrects the perspective. The results are claimed to look just as good as a photo scanned by a traditional flat-bed scanner. I haven't had time to check this out, but there is a physical limit that says you can't get any reproduction better than the original. So, I will wait and see about this.
You can select the name of the family tree where you are uploading photos and before uploading you can crop the photo, and "Edit Details" by using the icons at the bottom of the page to tag family members, date the photos, add a location and write a description. This also works for documents. So you could add the documents and citations to your tree as well as photos of people.
Quoting from Ancestry.com:
If you’ve enabled Shoebox in your phone’s privacy settings, each scan will be added to your camera roll. In addition, your scans will be added to the media gallery in your account on Ancestry.com (accessible with the same username and password you used for Shoebox).Stay tuned for a more extensive post on this app in the very near future.