Same as Matt, I use them to make the warmup time shorter. So I sort of kick things off with a couple of exhale holds, then do one pretty long one with full lungs, then max (instead of 3-4 progressively longer full inhale statics). I find that I don't need much other preparation. I can come to the pool stressed, heart beating, not relaxed at all, but with that first exhale I just sort of force my self to static mode again. I don't much look at the time, it's just to calm me down to get started...
The curious thing about my warmup, that I don't see many good static divers doing is that I actually do more or less 2 max attempts, the last one is just considerably longer
Ie, the last warmup is pretty hard...
