The website
My Digital Studio has a ton of great information and tips! It's worth checking out before you invest in MDS.
I initially got MDS because there are so many stamp sets included! I could print sentiments to layer on a hybrid card, or images to color by hand (love being able to resize or flip an image). Now I am saving a ton of money by buying the Designer Series Papers digitally and printing just what I want, when I want. I use Hammermill's Color Copy Digital paper to print the DSPs on and it looks and feels like SU's.
Good luck deciding!