Perhaps "sharp" is not the right description. <:) I meant that when you press a key down, it is possible to feel the edges of the neighboring keys. Your finger can catch on a key's lip (if you try) and flex it up. To me, it (literally) feels cheap and flimsy. I've only had two (Lenovo) ThinkPads, so I don't know if different models or IBM's models had better build quality.
That sounds strange. They keys on most Thinkpads can't depress far enough that you'd catch the edge of the key in the upper neighboring row. I just tried, and I can catch the edge of the key in the next row below, although I'd have to have my fingers pulling down on the keys to do that. That's part of what the key shape does - it's supposed to guide your finger to the center of the key and keep it from sliding off.
As far as the actual mechanism of the keyboards, almost all laptops (including Macbooks and Thinkpads) have used the same scissor-switch mechanisms for about the last decade.
