I thought I'd add my two bits to these miscellaneous discussions.  We
like the top bed in our 1981 Westy because ou don't have to move
all the junk around to climb in, like you do when you want to use the
bottom bed.
  In addition, the dog can't get up there. ;)

We have found that one of those egg-crate type foam pads that you can
get at any department store these days for about $20 really adds to
the comfort level that you get compared to the normal 1-2" pad.  
I trimmed a piece to just fit the bed, and it is thin enough that it
can be carefully folded and stored up there!
 
John