Is there a way to get textboxes, labels and other wpf controls in xna that supports margins, etc that flexes for window size?
Check out SQUID: http://www.ionstar.org/
It's a really clean, fast, and engine independent UI system. I've worked with it extensively and really enjoy using it. The download includes sample code for XNA 3.1, Truevision3D, and SlimDX.