Is it actually open, or is it Tivoized (i.e. DRM'd)? Is the vendor compliant with the GPL? Is it actually a named distro (whether a normal desktop one or a specialized one like Tizen), or some weird half-proprietary thing? Is there community support for it?

The questions I have about these sorts of things usually have nothing to do with hardware specs or features and everything to do with aspects of the system that aren't ever mentioned in the product listing. Frankly, I'm surprised that the product even mentions the words "Linux system" at all, rather than leaving it completely ambiguous about what OS it uses. Last time I was shopping around, which I'm now realizing was a few years ago at this point, it seemed like half the stuff might've even been running some kind of embedded Windows -- that's how unclear it was.