It's true that people with JavaScript disabled won't be able to run any JavaScript, but once they turn it on it should have relatively good feature support -- I suspect the sort of people who know how to disable JavaScript aren't using software more than 5 years out of date.
They are used to it? The number of users who have JS disabled is already small. The number of those users who lack the technical expertise to enable it as needed (and understand when that is necessary — e.g. with a blank or broken page) is probably many, many times smaller.
