@Dan: Good to know you have this kind of thing on the radar.
@Blowdart: That's the first complaint I've heard about KA, but I'm sure it's not perfect. I don't know the context in which this was expressed, but I can imagine that there's a ton of people trying to tell the guy how to do things right, and you can't please everyone. KA has been targeted more towards supplemental learning, IMO, so I would combine various resources. I also believe that over time, the best of the best will rise to the top, and we'll have a collection of the absolute best lectures/tutorials/exercises possible for a given subject. So we may end up mashing up various lectures together to form the ultimate lecture series ... but not without a lot of editing.