I have GemKit for VisualWorks 7.8 available. I'd like to get feedback from existing GemKit users to make sure it works for them. GemKit itself seems to work fine for me. I haven't upgraded the release management tools to the new version of Store since it seems more like Store improvements than core GemKit functionality.
You can download GemKit, some documentation on how to set it up and use it and two video tutorials from this location:
If you have any feedback, you can send it to me at firstname.lastname@example.org.