ACDSee Gemstone and ACDSee Ultimate are two different product lines.

Gemstone is built for people who are looking for an editor or a straight photoshop alternative. More specifically, Gemstone brings an MDI interface that allows multiple Photos to be opened concurrently. You can then copy, paste, and transfer edited elements in between photos easily. This allows us to expand into traditional layered image editing territory and bring familiar workflows to the users.

Edit Mode in ACDSee is a STATE-DRIVEN GUI. Once you are in one graphic tool, you need to confirm and exit that graphic tool before you can get into another one. Only one photo can be edited at a time. Switching between edited photos requires the user to save the current edits before opening the second. The workflow is different from Gemstone.

If you are a photographer, and you usually only touch up/edit one photo at time then ACDSee Edit Mode/Develop Mode is ideal. If you want to create something original by combining and mixing multiple elements from multiple photos you will want Gemstone.