I do the exact same thing. I find WIP stash-per-branch very useful when I'm context switching often between feature branches. I've got two aliases set up for this -- `git wip` and `git popwip`:

  $ git config --global alias.wip
  !git add --all && git commit -am 'wip'

  $ git config --global alias.popwip
  !git log -1 --pretty=%B | grep -q '^wip$' && git reset HEAD^ || echo 'HEAD is not a wip commit'