Below are three pictures comparing two similarly posed Howling Banshees. Both models were hit with black primer, the armour base-coated with Khemri Brown (Foundation Paint), had Devlan Mud (one of the new washes) applied, then hit with a thick Bleached Bone in all but the deep recesses. The model on the right was then given a watered down wash of Devlan Mud on top of that.
The second wash was watered down so I didn't lose too much brightness on the model as a whole, meaning that I didn't require a highlight. The wash really does blend everything nicely and gives a great sense of shading and depth for virtually no effort. They are a marked improvement on the old washes, and I highly recommend them.
I ordered a while ago the full set of Foundations and Washes. If you guys find the above useful or interesting, please let me know if you would like to see another foundation (or normal color) tested with a couple washes. I can use some of my old plastics sitting around in my bitz box ... as well as some old models from old board games.
[EDIT] I ran a bunch of genestealer arms painted red through every GW wash. See more here.