One thing that has been bugging me for quite some time with AucTeX (which I love, in general) has been that I wasn't able to reset the bloody hot key for math mode input.
The original setting maps to Shift-key left of backspace-space, since it's an accent key which I occasionally use for .. y'know .. accenting letters, and thus don't want immediate output from. And M-x set-variable LaTeX-math-abbrev-prefix didn't do anything close to what I expected.
Today, I, on a whim, go and search the auctex mailing list archives for this. And lo and behold! One of the first messages tells me that I need to do M-x customize-variable LaTeX-math-abbrev-prefix. So I do, and it has my changes already, but not committed, so after committing the changes I try it out and it just works!
This should speed up usage of Emacs for me a bit.