It's the strictly organic crowd that bad mouths MG, I've used it with good results BUT it is easy to overfertilize and it is very unforgiving if you do, I stay on the conservative side when mixing it and won't give my plants full strength until they are larger. Works great as a foilar spray. I like to alternate with some manure/worm compost/fish oil/seaweed tea and throw in about a 1/4 dose of MG about once a month. I think the organic material provides very beneficial micro nutrients.

I just picked up a large bag of MG potting mix I plan on using.