Yes, it is very much important. I would even say its highly critical. It can be your friend or your enemy depending on the situation. Although, like everything in poker, you can never be 100% sure, but it can be a strong indicator. Usually, when it comes to time, a person acting quickly can say a lot.
If someone pops with a big bet or all in within 1 second or two, more than likely, they got something big. Its not 100%, but then again, the reason why people bet big pre-flop with AA is not because its 100%, but because it has the best chance of winning at the time. If someone does take a lot of time, like more than 5 or 10 seconds, than it could indicate they have a weaker hand.
I would say, pay attention to the amount of time a person takes, but don't totally rely on it of course. There are people who will purposely take more time to make it seem like they have a weaker hand, and I know people who go all-in instantly when there really just
bluffing. But these are the exceptions to the rule. Just like getting your AA busted. Generally speaking, the amount of time people take Can tell you something, if they move fast, they got something, if they take longer they got a weak hand. This is my opinion.