For stupid, bureaucratic reasons, I have to have GRE scores for about half the programs I'm applying to.

That's surprising to me. I thought a GRE was required of pretty much all institutions for graduate level work, regardless of the program being involved with.

That being said, I just recently took the GRE and I have to tell you, it's not your average standardized test (I hate nearly all of them), the GRE is friggin' brilliant. I LOVED taking that test, even though it took about 4 hours to complete and I was exhausted afterwards.

I haven't done a single thing math related in 7-ish years. It doesn't matter at all. If you know basic algebra, that's really all you need to know. I think there might be some simple geometry things, too, but that's not the point of the GRE which is why I love it so much.

The SAT/ACT tests knowledge. The GRE tests reasoning ability. It's nothing like what you will expect out of a test, and it's probably why they require it for graduate schools because no other standardized test does that. The writing portion tests your ability to not just write clearly (one third of the points, probably), but your ability to identify facts, misinformation, and the ability to debunk incorrect facts and misinformation. The quantitative part doesn't test your knowledge of algebraic facts, but your ability to piece together solutions of something given information on your own. In fact, I don't think I recall other than a simple y=mx+b example them ever even giving you any algebra or x/y variables directly at all. It was all very unique word problems that involved very basic concepts tied together to see if you had more than an understanding of the base concepts and could improvise to piece together and reason your way through a complex task.

When you are getting a Master's in something, you aren't really (theoretically) getting the same type of degree as a Bachelor's. A bachelor's indicates knowledge about a topic, a Master's indicates proficiency and the ability to discuss and lead on a topic. So the ability to reason, debunk and prove facts, etc, is a necessary goal in a graduate degree.

I honestly don't think that you can really even study for the GRE. After taking one practice exam (they have a Java software package on their site for it, I recommend doing one of those) I realized this, and didn't study. I ended up not completely finishing the exam (I spaced out on the last part... it's LONG) and still got ~316 revised score.

While math might not be what your field is in, your ability to formulate a poignant argument and to improvise creative solutions to things is pretty much a universal thing for a graduate degree.