I wanted to add a link to Jeff Gorman's classic ramped shooting / shuteing
board, for those newer to the list:
http://www.amgron.clara
.net/rampedboard68.html

Jeff describes the benefits in his always straightforward and helpful way:

"The ramp has the advantage of extending the wear over a greater part of
the cutting iron. Also the start and end of the cut is gradual. Instead of
the whole (working) width of the blade entering and leaving the cut at the
same moment, there a gradual engagement and disengagement. At the start of
the stroke, this slightly reduces the bang and at the end of the stroke it
can reduce breakout (called spelching).
     The effective cutting angle is unchanged. The ramp gives the illusion
of slewing, but is really only making a diagonal cut with the plane
travelling in a straight line along its axis."

Brian
15 years later I'm still meaning to make one of those