In summation: Subspace is
the tool of BDSM and D/s IMHO. Doms and subs wishing to grow together can and should utilize subspace more than they rely on strict S&M or humiliation (also useful tools don't get me wrong). I believe the ability to enter subspace sooner, more easily, and stay in that psychological mindset longer should be the goal of every sub where as being able to withstand a certain number of caning strokes would be a goal set by the Dom and worked towards (for example).
ReallyGreen.