Glad you got it. One of my priorities in the coming months is to add tagging support and the ability to edit metadata through GSP, but I haven't yet started the code or designed the workflow. I am strongly considering Silverlight for the best possible user experience.
If you think any of your code could be useful to GSP, I hope you will consider sharing it. If I end up using it I will share some of the donations with you as a token of appreciation.
By the way, just as an FYI, there is already support for persisting changes in the metadata collection to the data store in the business layer. That is, calling GalleryObject.Save() will persist the contents of the MetadataItems property, so all you really need to do is wire up the UI.
Roger Martin
Creator and Lead Developer of Gallery Server Pro