These pens have been discussed in several threads on the board since they showed up in Houston....with mixed feelings and testing results. I'll stick with my Sewline pencil.
http://www.quiltingboard.com/t-85996-1.htm
http://www.quiltingboard.com/t-87043-1.htm
http://www.quiltingboard.com/t-94217-1.htm
http://www.quiltingboard.com/t-93330-1.htm