When a user takes an action, she needs immediate and clear evidence of its result. Sakai in particular often fails to provide this feedback. For example, a user in the Resources Tool may click on a folder low on a page and expect to see its contents. The contents are displayed, but not necessarily shown to the user, since the page reloads from the top, hiding anything "below the fold." Many actions do not provide "success" messages.
A slow process, such as a large file upload, should let the user know that something is happening and if possible should let her know how much longer it will take. When an error occurs, the user should see a message that tells her what is happening and what she can do about it.
This shades into situations where the issue is not feedback in the strictest sense but a matter of poor orientation and multiple design issues of workflow, layout, language, etc., that leave the user unclear as to the meaning of an possible action or where to begin/what to do next. This was the "WTF?" sheet at the summit and is grouped here under feedback.