I have it for me, and the whole family, as part of my employment benefits package. On the two occasions I’ve used it it has been very good. Both were for knee surgery.
My ACL diagnosis, MRI, consultation, surgery and physio all happened in a couple of months. It would have taken me six months at the time for my first consultation with a NHS consultant. That delay would have led to a longer recovery time apparently.
All of the consultations, scan and surgery happened at times that suited me rather than the NHS so I was able to fit them in around work. Also, I got a cup of coffee, an apology and a copy of the Times to read when they were running five mins late to do my scan. I doubt very much that would have been my experience had I been going through the normal NHS process.
If I didn’t have it through my work would I pay for it? Probably.