These are awesome looking! Nice work. I have a few experments myself that this would be great for if you're interested and wouldn't mind kicking around some ideas. Been looking for something -exactly- like this to use as a Xbee radio test bed for quite a while, but only found FIO , high end expensive dev kits, etc.
In regards to the design, I do agree about the USB port being alleviated- of course that is good for the pros and manufacturing $$$. But then again, if your target user is the weekend experimenter type home/hobbyist it makes things perhaps easier for the novice if there's USB. I would bet there is a lot of folks wanting to increase their Arduino knowledge base with a feature packed but small Xbee enabled board system like this to use for dev , not just me. The TFT LCD success is definitely a plus as well. Get in touch, i like what I am seeing here...alot! Could use one tomorrow if it checks out. Tired , myself, of reinventing wheels. Again, nice work. 