I've only read once and recently that they were the 'hariest humans' on earth. Maybe not, huh?
The photos I've seen show them as normal-looking people but the men wear long, flowing beards. I think their religious practice of not shaving as adults has led to an exaggerated view of their "hairiness." The sites I visited seem to combine a lot of myth with actual observations.
It's interesting that anthropologist Christy G. Turner III (of Anasazi/Toltec cannibalism renown), an expert on tooth shapes, did a study comparing the teeth of the Ainu and Japanese. His conclusion (some years old now) was that the Ainu teeth are similar to prehistoric Japanese (Jomon?) but that modern Japanese teeth are similar to those of ancient Chinese. I haven't succeeded (so far) in finding any investigations of Ainu DNA. Possible connections with the Caucasion mummies of Tarum, China, are intriguing but so far as I can tell no definite connection has been established.