Wasn't in the mood to open up the power supply.
I'm not a huge fan of
 using the AT power supply to begin with; I had to chop off the ends to
 stick 'em in .156" headers anyway (which I don't feel too badly about
 because they're cheap generic PC supplies, not an actual vintage item). 
    I use them in all kind of projects, and have no problems.
  I could use an ATX supply if I wanted to put a soft
switch in.  At some
 point, I'll have to make a board to wire up whatever supply I use to the
 .156" pins anyway, so why not?  They are, in fact, cheap.  But I also like
 the dedicated, fanless ones.  Sometimes it's a matter of aesthetics. 
    It is up to you, but ATX power supplies are cheap :) You don't NEED to
put a soft  switch. Short the green wire with a black wire, and key the AC
supply. It works :)