Well, I have had pretty good experiences so far. Not to be graphic, but hey, we are talking health issues here, so here goes:
I have had several infections in one of my breasts over the last year. The NHS was great, have done ultrasounds and all sorts of things. Unfortunately, there isn't much of a solution to the problem, other than surgery, which would mean losing all sensation in my breast forever, and which I am not willing to resort to yet. They think if I quit smoking it might help, so I am giving that a try. I have a consultation to help me decide how and when to quit next week.
I have psoriasis, and have been given even better medication here for that problem than I ever received in the US, and it has cost a tiny fraction of the price. In the States, I was paying up to $300 for two tubes of medication, here I paid £7. I also had several problems with my feet that 2 different dermatologists in the States said was due to my psoriasis, but my GP here actually ran some tests and discovered it was most likely due to an unsanitary pedicure ages ago. I was given medication and that has completely cleared up - no more pain! I had laryngitis last week and was given some antibiotics and they seemed to work just fine.
That is pretty much all of my experience with the NHS to date. I think a lot maybe depends on the problem, and whether it is very common or not. For example, my skin troubles are very common, so no problem at all. However, show them recurring breast infections from a woman who has never been pregnant, and it's a different situation altogether. At any rate, all they ever did in the US was give me antibiotics, so at least I have had some ultrasounds and things here. I can't complain. I could go for the surgery if I wanted to, so at least I have that option.