I can think of another: it lowers the seizure threshold. For most people this is not a problem but for those who have seizures or for those who have a low threshold and don't know it b/c they've never had one, it can tip you over into having them.
I'm one of the latter--they started in 1983 when the companies started putting aspartame in the sodas and stopped when I got pregnant and cleaned up my diet and I never went back to drinking them and never had another seizure. They were fairly frequent (like 10/year) before I stopped drinking the stuff. The problem is that nowadays it goes into many foods that you would never think to look for it in, but still seizure free here.