I'm just back from a domestic flight. I took a worn-down Imperial Barlow knife with my carry-on (paid $4 for it years ago). Blade length, including the choil, was under 6cm.
Naturally, I declared it at security -- all above-board, nothing hidden. A major airport let it through, no concerns.
However, a regional airport interpreted the new policy differently, and measured it from the pivot (like they do with scissors). So, it was 0.5cm over the limit. I was nice as pie, and surrendered it. At least I know what the hard limits are now.
Anyway, I thought some of you might like to know. BTW, box cutters and credit card knives of any length are still banned. They also grill you about US connecting flights (total ban on sharps remains in effect).