I think this is a bargain deal, for what you get. I also think I'm a little spoiled with magnetic stackable filters, to where these aren't quite as exciting for me as they used to be. But I can say that, if I were buying my first filter set, or if I was just used to screwing filters on. Or, I was trying to save money, or simply couldn't afford more expensive filters, I would call these a 5 star experience.
I saw another reviewer mention their being aluminum, and having a tendency to bind more than other materials. I've had that problem in the past, but not with these yet. Just something to keep in mind. Try not to tighten them too hard, and I've never done this, but I imagine it's a thing... I bet you can very lightly lubricate them somehow, being careful not to get it on the lens. Don't quote me on that, and maybe consult your doctor, lawyer, psychiatrist, professional photographer before attempting such a stunt.
Other than that, you are getting what you pay for here. I love K&F, and love the effect of their ND filters for glare and contrast, and a much more cinematic/professional look to your content