Time taken can be a tell on people in the long run, but like anything in poker there is no one size fits all motto.
My best advice is to never go into a table with a preconceived notion. Someone taking time can mean someone on a draw trying to think of odds
and such. An instant check can be someone trying to make you think they have the check/fold box checked. You can't know any of this until you actually study the person and can tell he kind of does something, but it doesn't hurt to know what to look for.