Most of the optimizing I do has to do with DOM manipulation and replacing slow generic library functions with native and/or custom-written ones. I've got a lot of low-hanging fruit to pick before I get to things like bitwise operators. Most optimizations I've seen are very language-specific and it can be hard to guess what is faster. Which is why profiling and a tool like http://jsperf.com/ are critical.
By the way, from what I've read bitwise operators aren't very efficient in JavaScript because of the overhead of conversion from generic duck-typing to binary.
You probably already know this, but your last sentence also has one minor advantage, in that you can use an otherwise pointless bitwise operation to strip off decimals, e.g. 100.919 | 0 .. => 100
By the way, from what I've read bitwise operators aren't very efficient in JavaScript because of the overhead of conversion from generic duck-typing to binary.