It's not just handy for scripts, I think it's imperative in scripts where you want to go in and out of a lot of directories.

  for i in foo bar baz; do
     cd $i;
     #... do something
     cd ..;
  done;

if "bar" doesn't exist, your cd .. will throw you off your original directory, whereas

  for i in foo bar baz; do
     pushd $i;
     #... do something
     popd;
  done;

you'll be guaranteed that after "popd" you're back in the right place to start a new iteration.