Value of information is zero. Do it if you are curious, or take the money and watch some movies with friends.

I found the WAIS helpful, but only because it factored it into multiple components and the structure of my scores was illuminating. (I had a severe discrepency between two groups of components, and very little variation within them)

Reminded me that I've never had an IQ test; is it worthwhile?

IQ tests are mostly useful for other people evaluating you. Compare to, say, taking the SAT without wanting to go to college. It's mildly useful for you to know how your SAT score compares to other peoples', but it's very useful for colleges deciding whether or not to admit you.

Most tests will give you your subtest results, so you can see "okay, I'm better at doing visual processing than auditory processing" or related things, but this will rarely be a surprise; in that case, you probably already preferred reading books to listening to audiobooks, and in the reverse case you probably preferred the reverse.