In addition to interacting with the panels, if you're using a supported browser, you can drag and drop straight into the editor. It will automatically figure out whether the uploaded file(s) are images or other files and add them to the appropriate panel automatically.
In IP.Board currently, there is a "My Media" button which allows you to insert content submitted either in other posts or elsewhere in the community (images in IP.Gallery or files in IP.Downloads for example) into the editor. In 4.0, this feature is found in the images and attachments dialogs.
Just with normal attachments, the content is inserted as it will be shown rather than the current " " tag.
Please let us know what you think of the uploading features in the comments. Remember though that we're only half way through our series on the 4.0 editor. In my next blog entry I'll be talking about customising the editor and the place of BBCode.