For the average person it’s pretty great. If you have something minor in the grand scheme of injuries you may have to wait a few hours to be seen, but if it’s serious you’re seen right away. In both cases you go home without having to pay anything at all.
Where it really fails is helping people with chronic illnesses. There’s still a lot of denial about women’s health issues especially so getting diagnosed with something can be impossible if your doctor decides “it’s all in your head”.
I obviously can’t comment on everyone’s experience, but for the few people I know that did get cancer (including my mother) they were all scheduled scans within two weeks and had results delivered within another two (or less especially for the first diagnosis).
In my mother’s case everything moved extremely quickly, due to the doctor suspecting something serious the first scan was scheduled in a few days and the results were back before a week had passed.