I also know the problem with the interference of shortcuts... but I haven't thought about handicapped people, which have to use a screen reader or a braille interface. As far as I know they have special plugins/tools, which parse and filter the content before they "see" it. So these tools - I think - filter also the accesskey shortcuts so they don't interfere with the generic shortcuts of these people.
Accesskeys are especially for admins very useful because when they begin to built a site with mp, they have to do a lot of monotonic actions like "change, save, see the result, change, save, ...". For such actions accesskeys are indeed very useful. Also wikipedia.org - which surely don't wont to exclude handicapped people from using Wikipedia - uses accesskeys. Maybe we should implement accesskeys just for admins? Many professional users rely on such stuff like accesskeys and web applications like Google's mail service, that want to replace classical mail clients like Outlook or Kmail, uses accesskeys too. But however you're the chief architect! ;) Everybody can implement the accesskey feature in it's own installation of mp.
Thx for the links! The "skip links" feature is very nice.