Andy Powell has some valuable feedback on metadata as well as repositories, extrapolating from his experiences with music at blip.fm as well as spotify.
I agree with an estimated all all of what Andy mentions, including the importance of

social activity around content;
a resource oriented approach;
a REST based architectural style;
designing on behalf of “residents” rather than “visitors”;
linking to related things;
…


BTW, this is a very slideshare friendly kind of slideset. I am not sure how well this style works on behalf of a presentation, but it certainly makes it very easy to follow the train of thought. Maybe, in Andy’s words, this style is more “of” the Web than just “on” the Web…
In any case, there is lots of Food on behalf of Thought here, on behalf of developers of institutional as well as learning object repositories alike! Would be great if you would share your thoughts in the feedback here…