The KFF is a breakthrough in the price range. Ergonomics are fantastic, steel is OK for a "pure fighter", and once the LAWKS is manually tripped, lock strength is excellent.
However.
They're budget linerlocks. If the LAWKS isn't tripped, the linerlock can fail. The LAWKS prevents that, but it's an extra manual stroke you may not have time for if it's a real "Quentin Tarantino moment".
You have to practice a cut as the initial move in a high-speed mess. Once the LAWKS is tripped, sure, it's as good a hard-target stabber as they come.
If your budget is $50, bingo, look no further. If your budget is $80, it's still a good buy although not the only option.
If you can afford it, the Carnivore is in my opinion the best fighting folder for "cannot hit 4" legal climates". You get everything the CRKT KFF gives you, plus better steel and better peak lock strength without the need for a second manual-action safety lever.
If you're in California, TX or any "no length limit" situation on folders, the Sifu is the current king.
(Note: the Point Guard also has the LAWKS, but the grip shape can get you in trouble of a different sort: "slip up" accidents on a hard-target stab, where you cut your own fingers due to sliding off the grip. The KFF absolutely prevents this, as does the Carny, Sifu, some others.)
Jim