The unemployment rate as a measure of recessions

I wonder if it is as good a measure of economic severity as it used to be.  The greater the heterogeneity of the labor force, the greater the potential for underemployment.  Even if the downturn is bad, I am not sure unemployment will stay above ten percent for long.  New search and matching technologies, such as found on the internet, might create quicker job pairings, albeit with continuing underemployment.  Unemployment is of course important but let us not view this category in purely binary terms.