it's good stuff, but it's not the only stuff. i don't like straight neem oil, but at .9% it's good in garden safe fungicide 3, which is both a fungicide and pesticide. it's not OMRI, but it is organic rated.
i keep a bottle around, mostly for my outside plants, but it works pretty good on powdery mildew, which is occasionally a problem with young seedlings or cuttings.
actually, a teaspoon of dish soap and a teaspoon of cayenne pepper in a quart of water used as a foliar spray will kill most common pests, even spider mites, if you catch them early enough.