Doing some materials testing so I can start doing some home publishing for my little games. I think putting in the elbow grease allows me to cut out some of the POD folks and to, ultimately, save on shipping costs.
I learned that 42 pound (link) works great for internal pages. It doesn't show the other side and does a good job stopping marker bleed from the other side. I used Pentel markers for it and was surprised to see how it stood up to the ink.
So, yes, I'll be using these for internal pages. I think 80 pound will be really good for covers.