Hey, I’ve got no problem with talking about it right here in the community! This is where I’ve learned to build and use it, this is where I’ll share what I can. 
Functionally, as far as the x-carve’s operation goes, I do not see that much of a difference. It worked well before, it works well now. There would likely be a far greater operational advantage for a heavier CNC unit, or one using larger steppers, given the bigger, more powerful stepper drivers.
The major advantages I see:
1: Installation. The header crimping and soldering of the header to the G-shield was the most “technically complex” part of the X-carve assembly, and required the most skill on the part of the assembler. I had done PCB soldering and crimp fittings of that sort before so it was not a major challenge to me, but someone who had not might easily have had difficulty. The X-Controller’s very clear, simple labeling of the plugs, and screw-down terminals make that job the work of minutes with a screw driver instead, and there’s no longer any question of wiring order in the header, particularly. Additionally, the only part of my X-Carve that required any modification to assemble properly was the housing for the Arduino / G-shield. On mine, I had to cut an eighth inch or so of the window bottom away to allow the header to stand clear of the wall, and the G-shield to seat correctly. Problem solved!
2: Individual grounds. Following up on #1, one of the more standard things that I’ve seen and that I personally experienced with the stock set-up is the number of wires that need to go into a single ground connection. Splicing several together to a single wire, then installing that one seems to be the common solution to the problem. Again, soldering and some level of technical knowledge is required. Again, eliminated by the clearly-labeled X-Controller ports and the designated grounds for each connection.
3: Serviceability. Having the Arduino and G-shield either not properly connected together, or coming loose seems to be another common point of failure. Integrating them both into a single unit cleanly eliminates that problem.
4: Integrated E-stop. This has already saved me a couple times during setup, and is much easier to use than hitting the switch. These can easily be put in-line, but having it right on top of the controller, right next to the X-carve is tremendously handy.
5: Stability. The old control unit, as it was provided, had an extreme tendency to wander around on whatever surface you set it on. It rested only on a pair of screw heads, and the smooth metal base of the PSU. I added rubber feet to mine, which helped to an extent, but it still had a propensity to walk on the bench over time. Not so, the X-controller. Where you set it, there it will stay!
6: Professionalism. This doesn’t really matter much, except in a rare few situations, but it sure looks a LOT more professional. No more rats-nest of wires going into three sides of a stack of differently-coloured, miss-matched boxes randomly. Now it is all neatly lined up in rows, in plugs, and all to one side, meaning you can set this somewhere with the face exposed, and not have a tangle of cables in all directions. And it all goes into a single, professionally-anodized and silk-screened enclosure. It looks like a professional unit, instead of a home-build.
7: Power. Having all of the steppers driven off of their own separate drivers with plenty of juice means no fiddling around with your G-shield pots to get your NEMA-23s to stop staggering from a low-current condition. This one just works, right out of the box, no fidgeting.
8: Expansion. I can’t speak to this one directly yet, as I have not actually had a chance to install and run the AC Relay Box (planned for this weekend), but having the capability to directly control external devices right off of the control unit adds a tremendous amount of functionality. I’ve come up with quite a number of potential uses for that, ranging from the obvious AC relays, to solenoids controlling pneumatic clamping or linear actuators. How neat would, say, having your enclosure automatically close, and your dust collection and spindle come on by themselves, controlled in the code? And having a proper connection for the Z-probe is very nice!
I’m sure I will think of more as I go along, but those are the ones that popped to mind immediately. I really am enjoying it!
