Morii 说:
Almost never feel the need to chamberblock outside of a duelserver, and even there I rarely do it. In (serious) battle in 90% of the cases its not worth the risk. And in the remaining 10% I basically only do overhead and stab-chambers.
Truly no offense intended, but it just seems you lack the confidence in your ability to chamber. People develop habitual methods of fighting and exploiting that is highly advantageous. Even when I'm using a sword and board I exploit people tendencies to overuse a particular swing.
Morii 说:
Also a tip: Don't chamber more than 1 time in a duel, unless you know your opponent isn't very good(smart). Because if you meet a skilled and reasonably intelligent opponent he'll see right through what you are trying to do only by looking at how you move, and he'll just hold some of his attacks (hitting you extra hard due to the extra damage held attacks do).
Anticipating the hold is just a part of chambering. It also gets difficult when you fight the same people continually as they are now expecting you to chamber...so you must get creative. Also, as stated before, people's habits while fighting. Exploiting their patterns. And as Plazek points out just swinging may get them if they hold too long. Seen it many times.
I think it's really just how comfortable you are doing it. It's nothing amazing, just another arrow in the quiver. And I don't feel it's really a difficult skill as it's the same reaction as blocking, just scarcely utitilized by the masses because it's unknown/misunderstood.