I've got a whirlwind, and it is a very nice knife for the money. Compared to the action of my benchmade apparition (also assisted opening but by a different mechanism), I would say that the whirlwind is slow. However, it never fails to lock the blade, unless something gets in the way of the blade as it is swinging open. The lock is a liner lock and I've never had it disengage accidentally. It disengages easily, and does not hurt my thumb, unlike my apparition (also liner lock). I've also found that although it has only a singe thumb stud, the holes in the blade give sufficient purchase for ambidexterous opening (unlike the apparition), and I can close it with my left hand without getting my thumb in the way of the blade as it is closing. I also prefer the knurled thumb stud of the whirlwind to the smooth pyramid thumb stud of the apparition. My whirlwind is several years old, and has developed both lateral and vertical blade play. It mostly sits in a box now, but it came new with a scarry sharp blade, and after untold sharpenings, it is as sharp now as it was then. It got sufficient use when it was young that the torsion bar broke. An e-mail to kershaw and and a week or so later I got a new bar for it (free of charge). Disassembly is easy enough and you really can't beat the service. If it were not for the other knives waiting in the wings for pocket time, I would buy another in a heart beat.