A picture of it is attached in my first post. I don't know if I'd call it "good" but I've seen worse. The average returned value on the display is 4000 something (although it bounces around and rarely stays on that number). 4000 something RPM would be 75'ish RPS when it should really be about 10 so it's triggering about 7 times more often than it should... and everything in between. I'm wondering if there could be a DC offset, shifting the wave too low or too high.
Oh shit, just had a thought... what if I feed the input into the comparator pins and then output a square wave from the comparator to the interrupt pin? Then I could set my own threshold voltage?