https://bugzilla.wikimedia.org/show_bug.cgi?id=42394 Wikipedia articles can be very large as you know. There have been some reports that after the introduction of landmark roles in mediawiki, navigation has become much slower for users of VO. It seems that this is caused by the fact that there is now one huge main landmark role around most of the content, that takes very long to finish indexing and in the mean time Safari is reporting 'busy'. Without landmarks, the page seems to go trough a different analysis path, causing way less resources usage. A good example is the complex page: http://de.wikipedia.org/wiki/Deutschland
<rdar://problem/14714484>
Also, it seems that Firefox is considerably slower than Safari, and Chrome 28 is fast but ignores the landmarks altogether (but in performance is equal to Safari when the page had no landmarks)
Still not really speedy, and worse, VO is not really telling you that it is waiting to finish the process of 'indexing' the page.