To me it's a no-brainer. Sure, $400 isn't cheap, but as someone said you can sell your existing DMD for $100-$150 if it's in good shape. So that helps offset the costs.
They are well made and well documented so they are very easy to install. Plug and play and go. Other than revamping the whole backbox to put in an LCD a-la WOZ or Hobbit, it really helps update the look of the game to modern times.
Jaz