* You can't add location information to images. Picasa web albums, which still is there, can do it and it'll reflect into Google Photos, but that's an extra roundtrip.
* STILL no dupe detection. That's sad and mad.
* Google Photos's new "Assistant" has a fun time taking everyt RAW image I've uploaded and turning it into a motion video with the associated JPG in which barrel distortion is corrected.
* No face detection for me. None. Zip. Zilch. Also no way to tag new faces on the web.
* If I create a sharing link for one image it'll link to an almost blank page with a thumbnail of my image. For any single image share it'd be much better to link to the image directly.
* Collections have an upper limit of 2000 images. I took that many of my kids in their first week.
* The editor has seriously lost its luster going from Google+ Photos to Google Photos. No more layered editing, no more manual corrections. That's also sad and mad.
* Google Photos -> Google Drive is a one way sync. There's no way to move a Google Drive saved photo into the Google Photos folder and have it shown in Google Photos. That's highly inconsistent.
* Same for deleting. Deleting a photo in Google Photos will delete it from the Google Photos folder in Drive, not the other way 'round, though.
* Uploading a 13MP photo with "Originals" setting will count against your quota. Uploading it with "High Quality" will store a compressed image and not count against it.Uploading any photo, even if it's under 16MP with "High Quality" setting will compress it.
* Same as with location, all metadata needs to be edited in Picasa Web, can't be edited in Google Photos.
* No "cast" option in the new Google Photos app for Android.
* Any action will result in a scrollback. Example: scroll down to April 2014, open a picture... have to scroll back down to April 2014.
[Will expand as it happens]