Yes, I've known lots who've done it, including one of our children. Really though, you have to look at the individual schemes.
Some are at the relatively commercial end - some developers & some councils (councils will sometimes use this system for residents with disabilities or other special needs). Others are with Housing Associations of vaious kinds - some aimed at particular people (key workers for example) others at residents of a particular area, and some are historically associated with various organisations.
Broadly speaking, in a market where houses increase in value (which historically they do) it can work well. My son got a mortgage for 50% of his flat, and so when it was sold for £150k more than the its original value, he took £75k into his new property.
Do check who is doing the valuing and the selling. A reputable Housing Association (and they mostly are) will have access to an independent valuer and a formal process. Certainly none of those I have known have had any quibbles.
I think a lot of people prefer to buy outright, but if you cannot afford a reasonable place to live otherwise, then it can be a sensible option.