I'm 61.5 inches tall, and ride a Trek 47" wsd with 650 wheels. It seems to be a perfect fit for me.

It seems smaller than my Titus MTB, which is a small frame, and with that bike I was also torn between S and XS, and went with the S because XS was a different frame, (but my frame got recalled later, so I didn't end up with it anyway) and I feel a lot more stretched out on the S, not in an uncomfortable way, but I think I'd have more control over the bike if it were smaller.

Nanci