We have had a futon for about 8 years now-have alternately used it as a bed
and a couch-and have found it quite comfortable for both purposes (though
now we have a house and a queen-sized bed, but my fiance was just out of
school in a one room apt.  when we needed it for a bed!).  We got the
thickest mattress available (there are different sizes and thicknesses)
and it's worked great.  It's been a couch for us for years.
 
Good luck!
 
-april and her boys
[Posted in FML issue 3537]