Yes, test stress is definitely an issue, and I don't want to be accused of adding to it. However, in the spirit of cold, hard reality, this article from the Wall Street Journal on use of SAT scores by employers deserves some attention. Whether you agree with this or not (and the HR department at Google has clearly decided to disagree, for example), there are still many big corporate employers who use the SAT as a convenient proxy for an IQ test, which relatively few Americans have ever taken. Whether IQ is a good predictor of job performance is a whole other mess that you can put in a college essay if you've researched it, but which you really can't do anything about as a high schooler (or parent of one, unless you're also a Ph.D-level researcher in psychology or management science).
That said, when you break it down, the SAT has a lot in common with an IQ test, and that's worth knowing. It's best not to really think about it as a test of reading, writing and math. It's a test of logic and fluid reasoning abilities administered through the filter of reading, writing and math, because you have to have some content on which to test intelligence. (If you love that idea, great! If you hate it, take the ACT, which really is a test of verbal skills, math and science.)