I'm very sorry for your loss Cory. In an objective answer to your question, however:
I'm happy to say I've experienced no real NHS horror story, and on the contrary, have many NHS anecdotes about hospitals which have saved the lives of loved ones, including both my parents in dramatic situations which needed intensive care and long, complex operations. The NHS provided them with good after-care that enabled them to make full recoveries and return to full-time work. The real cost of their treatment, if paid privately, would have crippled my family.
My grandparents have also all received life-saving and enhancing treatment and operations, although they have suffered from poor nursing care on rehab wards because of shortage of staff. Generally it seems - for the elderly at least - that the initial operations/blood transfusions/emergency treatment are great and effective, but the recovery/rehab treatment is lacking. For our family our elderly members have always been better off recovering in their own homes with visits from district nurses, wheels on meals and bags of family support (less infections, home comforts, quieter and more conducive to rest).
Not horror stories as such, but a typical bad example might be my sick and disabled grandfather being left uncomfortable in a hospital armchair for several hours, because of a shortage of nurses to put him back into the bed. However, I feel for the elderly who don't have family members to look after them and therefore no choice of recovering at home.
The one time I've given birth was great, the hospital facilities and staff couldn't be faulted, as was the post-birth midwife service I had at home. During pregnancy I found all of the relevant hospital appointments - scans, blood tests, consultants - to be efficient and satisfactory.
My poor experiences are almost universally with GPs rather than hospitals: a family history of inattentive GPs not making several serious diagnoses for family members, over a period of months to years, severely risking their lives. Or GPs not being open to trying new, updated treatments for family members with a chronic health issue.
I have been lucky enough to have had NHS dentists in the past, and that was great.
I think 'horror stories' is a big of a strong term for me when it comes to the NHS. The NHS is too big and too varied - by region, by sector, by Trust, by department - for even one person to cast a 'positive or negative' judgement on it.
I must say I was moved by Danny Boyle's tribute to the NHS in the Olympics Opening Ceremony, and, as someone who has lived in and experienced healthcare in many different places around the world, from basic developing world countries to superpowers to small and affluent European States, I value our flawed-but-indiscriminatory NHS more today than ever before, and I would fight for its existence, if I knew how!
From the cradle to the grave, they are there for us...