[noggin]

Yes, the actual 10bit display is not so important; many displays are incapable of this anyway; I myself have nothing that supports it (although my laptop *is* available with 10bit display).
10bit colorspace is important for intermediate processing of animation, i.e color gradients which otherwise tend to develop color banding.
There's no perceivable difference for most live action visual meida, afaik (well, except maybe some dawns-sunsets).

You usually see it most on saturated colour gradients - blue skies are a killer. Even in the 80s Quantel were using dithering to mask 8-bit limitations with their Dynamic Rounding technique, which Sony licensed for use in DigiBeta too. I think the broadcast industry had realised 8 bit was only just about 'good enough' and not brilliant, which is why we went from 8-bit parallel digital video (on 25 pin D-types if it was standard 601 over 656) to 10-bit SDI in the early 90s, and why DigiBeta supports 10 bit (but earlier digital decks didn't ISTR)

Yes - it has benefits in processing and compression too (you get lower bitrates for a given PSNR if you use 10 bit rather than 8 bit sampling, as the greater bit depth helps reduce compression artefacts' visibility), but there are definite benefits on some content even if you don't use HDR techniques.