Steve...
There isn't a crosshair. The bottom of the large hole is counterbored (stepped) to allow positioning a plastic reticule disk. To ensure accuracy a blank disk should be stuck in place with a tiny amount of something like silicone at three points and only then marked with something like a V-bit.
The software is set up to allow normal use with a reticule in place.
One other thing about the software - it's set up to auto-detect inch/mm operating mode, so if you have a project with metric dimensioning, the SuperZero shouldn't present any problems.
As for supply, no worry - I have about 90 of 'em on the shelf, so there's no danger of a shortage.
...Morris