Using numbered list element for navigation bars

We came across a website that used the numbered list element <ol> for its navigation bars (numbers hidden by CSS). It was really useful for our blind colleague who was able to identify how many links in the bar, whereabouts he was within the bar and, more easily remember where the useful links were. There was no difference to visual users

I can't see any disadvantages to using the numbered list element for navigation bars and wonder if it should be a recommendation to improve accessibility for blind users - i.e. does it really help all users of screen readers or will some people find it annoying?

Richard Warren
Userite
http://www.userite.com