Knowing Steve is behind this, I'd feel safe using the service. However, like most other road warriors, I have more miles than I can use, so buying miles just for the sake of having them doesn't appeal to me.
Knowing I can get 50+ miles per $1 spent buying magazines is an appealing proposition, as I read a lot of magazines (anything's better than SkyMall!) but I'm lazy enough I don't want to wade through the Raddisson/Goldpoints/ValuMags noise to figure out how to make it all work.
Given that, I think I'd buy into the service Steve & Matthew are offering if I could get some of the magazines sent to my home. :-)