I'll add in a link to one of my favorite threads here at E-Budo: Ryuuha Bugei all soft and mushy, too!
The thread includes excerpts from the article "Off the Warpath" by Karl Friday, professor of history at the University of Georgia and menkyo kaiden holder in Kashima-Shinryu.
I'll elaborate: Underneath the whole "to spar, or not to spar" debate are certain assumptions about the goals and ideals of traditional JSA training. The linked thread/article addresses that issue.