You are really blowing it here. The hub-like integration here was a key selling point for me. I don't WANT to have to launch a billion different apps to send / see photos in the various places I have and put them. Flickr, facebook, skydrive, those were a big three, and the existing app should have had share-out capabilities to those services (the 3rd party ones don't work well and are mFugly).
Do not make the mistake of forcing users into the multiple-app world of iOS and android. That's a step back we don't want to take.
As others have pointed out, your logic is flawed (and, my guess, complete BS) in claiming that outside apps have taken up the slack so integration isn't necessary. There are a dozen or more basic photo editors out there offering the same junk filters and presets. There was zero need for your teams to spend time on that.
Integration plus basic metadata editing (tagging, face-tagging, captioning) are the holes in the current photo app ecosystem. You had the first of those well in hand. Now you've blown it.
If you want to know why reviewers keep ridiculing windows 8, it's because the apps your producing for it have lousier functionality than the standard apps of 5 years ago.
Seriously bad move.

