The UI for setting folders seems quite clunky:
1) Cancel is unnecessary. Cancel is the back key.
2) The checkbox tap zone is quite small and if the folder has sub-folders you get navigated away from where you want to be if you miss. I'd suggest that the activation area for the checkboxes should be the full height of the row and square.
3) Remove from Folder is redundant. Simply uncheck the box and hit Set Folder.
4) Unchecking the box and hitting Set Folder doesn't actually save the folder de-assignment.