Looks good. Since you have quite a bit of space left over, it would be useful if you add 3.3V <-> 5V support for shields, so that it's all-shield-ready out of the box, something that would obviously add significant value to your board. If you use a level translator like GTL2000 for this purpose, it would only add a dollar or two to the BOM cost.
There's a discussion going on about this over here: http://arduino.cc/forum/index.php/topic,136717.0.html