I have a machine that was built using the same C&C pattern:

It's based off actual European Jamma cabinet plans so it's pretty authentic. It's not just a square box like other kits. I bought it ready made and then customised it with a PC, new buttons and new joysticks, as well as some other improvements.
I would say that there's not as much room inside as you would expect due to the plinth at the front (where the coin box normally goes). I've mounted my PC on a board vertically, velcroed to the right hand side of the cab. I imagine you could install a normal shelf in there with a smaller PC though (Mine's full size so takes up a bit of space).
Where the coinbox would go is a door, which didn't come hinged - it was just a flap you took out - so i sanded it down and put hinges and a handle on it. There's enough room inside to store my wireless keyboard and a separate trackball controller.
I would say the control panel is a little bit cramped underneath with two joysticks and six buttons. I want to put some servostiks in there but I think clearances might be a little tight underneath. It might need some extra routing out. The control panel has two big metal spring clips holding it down. Flip them up and the panel comes off.
The top part of the back of the cab is detachable for maintenance, but that means if you've got any kit in the bottom of the cab you have to lean inside to fiddle with it. It wouldn't be difficult to make that access panel bigger if you have woodworking skills.
The cab has two big rollers at the back and handles cut out at the top which makes moving it really easy. Just tip it back slightly and it rolls freely.
I love the look and feel of it. It's a great piece of furniture, and gets a lot of good remarks from visitors.