El Tint-o does just one thing (but it does it extremely well). It places a semi-transparent background behind your RapidWeaver content. Many themes are now including full-sized images in their backgrounds and El Tint-o will allow you to customize the way your pages look on top of those images. You can use rounded corners as well!
El Tint-o now allows you to select ANY color and display it with ANY opacity between 10% and 90%. And the setup for these is drop-dead simple... two sliders!
The stack works equally well in original Stacks or Stacks 2.0