It has been decades since I've bought a pocketknife--Instead, I've relied on the blade from my Gerber multitool.
My current job needs a knife frequently throughout the day, so I wanted something that would open quickly and easily, and that would clip to my pocket. I was initially set on an assisted opening knife, but after playing with a Gerber Liner Lock that was on clearance at Walmart, decided it was good enough for what I wanted, at a very good price.
I was unfamiliar with the modern liner lock system, although long ago I've had knives with the type of lock they evolved from. The older style was a traditional pocket knife, where the blade was held in position by a spring on the spine. These required some effort to open and close. The lock was a brass-colored spring that snapped into place when the blade was fully open. The lock did not rigidly hold the blade in place, but it did prevent it from closing unless you pushed the lock aside. One problem was that the pressure would suddenly decrease as the blade began to close--this could catch the finger pushing the lock aside if you did not maintain a firm hold on the blade while closing.
Until I experimented with the knife I bought, I was not aware of how much better the modern liner lock system is. With the liner lock, the spine spring is removed, and its functions accomplished with a ball detent and the lock itself.
The blade is held in the closed position by a tiny ball detent, with the majority of the pressure removed after the tip moves a quarter inch or so. There is little friction until the blade reaches the full open position, when the lock snaps in place. Once the lock engages, the blade is effectively a fixed blade. Because of the greatly reduced friction in opening, the thumb studs easily generate enough force to quickly open the blade, either with only thumb pressure, or with both thumb pressure and a wrist flick.
One-handed closing is much safer than the old version as well. When the lock is pushed aside, resistance is low but constant until the blade reaches the fully closed position. The back of the blade has a raised section with a tooth pattern. This naturally allows the index finger to easily close the knife up to about 45 degrees, although only a small amount is necessary. At this point you can remove your thumb from the lock and use it on the thumb stud to finish closing. Closing the blade beyond 90 degrees with the index finger along the back is difficult. Additionally, even if your thumb were to remain in place, the first part of the blade to contact the thumb is a notch behind the sharp part of the blade.
I am not thrilled with the easily-damaged black paint on the blade, and I wish the pocket clip was reversible, so I could more effectively carry this in my left pocket. However, for the price I'm happy.