Which ones? You have a source of information on that which we can consult, yes?
Rummage around on The Discovery Channel website. They did a show a couple of months ago about a kid that went blind when he was like 2, but he does this echolocation pretty well. Scientists say on the show that it’s pretty good.
Here’s some video of him from CBS (kinda grainy)
http://www.metacafe.com/watch/779704/best_video_of_the_year_blind_kid_uses_sound_to_see/
Ah here’s another link with a different guy
http://www.worldaccessfortheblind.org/2005/09/daniel-kish-using-and-explaining-echolocation.html