Alrighty, I had another poke at things and here's where it's at.
I moved the voltage regulator to the other side of the PCB, over near the power switch.
Added 10uf cap to the output of the vreg.
Added 0.1uf cap near the voltage reference.
Added input protection stuffs.
Added some vias here and there.
Ran the GND trace from the voltage reference directly to the output jack.
Let me know what you guys think.