I've heard nothing about 5-methyltetrahydrafolate coming under fire... I can say using the active form really did help me, as opposed to folic acid. It's not very useful unless balanced with b12 though..
I learned a lot at this site about folate, b12, and other nutritional connections (including potassium) with the b's here: http://howirecovered.com (articles and blog of a guy fighting Amalgam issues)