It is available on the BBC iPlayer at the moment. I've watched the first three episodes and they are very good at creating a strong sense of tension and suspense. They also probably contain a fair degree of worrying but generally hidden truths about the NHS ie. that some nurses are more competent than junior doctors and even senior doctors get tired and make big mistakes. There is a lot of fairly gross surgical procedure too. However, having said that I don't think the basic premise is anything like realistic (ward sister assumes the career and CV of a doctor who has gone to New Zealand). In that sense it is far-fetched.
I also watched it to see Jodie Whittaker who is clearly a good actress. But I really don't see her as Doctor Who.
It's been a good series. Looking forward to the final one, although a lot of recent series, like The Replacement, have ended disappointingly. Jodie Whittaker and Sharon Small are both excellent. Yes, aspects of it are far fetched but necessary for entertainment purposes.