Well, just like any other biological information we use to help us diagnose/point out specific issues we can sometimes get caught up in the methodology and loose sight of the reason we're tracking said sign
Examples:
People who count calories and weigh themselves every day when trying to loose weight can become obsessed with both.
People who check blood pressure for different health issues...
Those charting temps for fertility purposes.
Charting temps is an EXCELLENT measure of biological health and can give you a lot of information about what's going on in your cycle. Not only can you tell when you are ovulating, you can see if your body is maintaining enough progesterone (the hormone that makes your temps rise after ovulation) through the luteal phase, and if said luteal phase is definately long enough to sustain implantation.
When you do get pregnant, you'll be able to pinpoint the "implantation dip" where your baby implants in the uterine lining (your temp will probably drop slightly that day, then rise again) which helps to date your pregnancy.
But just like those counting calories or weighing themselves every day, remember to put that information in it's proper perspecitve. Try not to get obsessed by the information you are accumulating (especially at first!)
And also remember, when you aren't trying for a baby, charting temps is a great, healthy, drug free way to avoid pregnancy too!