Hey, Rachel!
Yeah, I've seen you gist before. In fact, that was where I started to understand the problem and imagine a solution. But what I'm trying to solve here is mostly the behavior of the "all-[NAME]-sprites" mixin, as you yourself pointed out as the remaining problem at https://github.com/chriseppstein/compass/issues/1005.
Anyway, your gist solution is awesome to solve this problem, but if you have many sprite maps on the site you would eventually end up with lots of code for each of them to work.
Both solutions, however, should not be necessary if there was some kind of option to do so from the core. I made a pull request to Compass that, if accepted, would do just that. You can find it at https://github.com/chriseppstein/compass/pull/1448.
Thanks for the answer!
Hey there, dc2!
So, I just added a "Step 5" to this tutorial to help you out with this. If you still find some problem to use it, please let me know! Also, feel free to contact me on my (newly recovered) Twitter: @cnstntino.