Constructive criticism sought

So I like this x-axis design :[www.thingiverse.com]. The dual-X carriage idea is pretty nifty. Only problem is that I would need to break out some pins and solder up a drive board for the second X-axis. But with access to cheap PCB's from Hongkong I could make my own board, which would be much more satisfying. I could have just bought a RUMBA, but where is the fun in that?

So I whipped this up to give me a second axis.

The Chinese Spring Festival is ending soon, so I have some time to play with the layout.

Any thoughts/opinions/criticism are welcome and encouraged.

Thanks in advance!