Well, this definitely caught my attention...
I really don't care too much about custom plays, but I need to be able to put together my own custom playbook from existing plays at least.
Now, I just did a google search trying to find info about create-a-playbook and this article is the closest I found:
http://cheatcc.com/xbox360/rev/maddennfl11preview.html
"In the past, players could start with their favorite offensive or defensive playbook and alter plays, select new ones, or even create their own play to save and add it to their custom playbook. Madden 11 allows players to start from zero. A single play can be selected and you can build an entire playbook around it."
Kinda sounds like they're incorrectly using 'custom playbook' instead of gameplan, but I really hope they know something we don't. The ability to create a playbook is the last gen feature I miss the most.