I just got an XU Lite and was amazed at how easy the eMMC install was. (Great job ALALRM folk!) I did the following and everything worked perfectly.
1) Buy XU or XU Lite and an eMMC flash for it from Hardkernel. The eMMC comes with a MicroSD adapter and has uboot already installed (on a hidden partition).
2) On another Arch install, follow the standard XU or XU Lite installation instructions, installing onto the eMMC via the MicroSD adapter. Except: Don't do Step 3 (uboot is already on the eMMC) and delete each of the existing partitions from the eMMC before creating new ones (I did this using "d" in fdisk).
3) Following another poster's advice, I also edited /boot/boot.ini and commented-out the "run verify" line. I don't know if this is actually needed.
4) My XU Lite came with the physical boot switches in the correct position for eMMC boot (both in the up position). But, double-check this.
5) Plug the eMMC into the XU or XU Lite, power-on, and be amazed.