I use them whenever I need to. Often I don't need to, since a compiler should be able to optimise the very basic things. Optimising prematurely is a good way to stuff something up (see question 5 here: http://ridiculousfish.com/blog/posts/will-it-optimize.html) And it hurts readability.

I would expect most good programmers to know at least some basic "tricks" though (and would hope they have the sense to not over use them).