Personally I rely on good gardening practice (or at least the vague hope that I might get round to it one day
) and the local wildlife to deal with my pests.
I cover my brassicas with environmesh netting to stop the butterflies and white fly making it home. I then plant out some extras (there's always plenty spare as I prick out most of the seeds that germinate) for the caterpillars to eat (and the chickens to pick at in winter). More caterpillars in the garden means more birds which in turn help you to deal with any caterpillars, slugs, aphids, etc.
I grow my carrots and parsnips in a raised bed which seems to stop the carrot fly from getting to them, sometimes I also cover them in fleece.
I don't cut down anything (unless diseased) until well in to spring so that as many ladybirds, lacewings and other beneficial insects have somewhere to sleep during the long winter.
We also have bats so a bat box (or 3) encourage them to stay local, and plenty of trees and hedges for birds to nest, shelter and feed from.
I let the chickens on to the veg garden during winter to find as many slugs as they can and then go out in the summer at night armed with a torch and a pot of salt (or with wellies so as I can stamp on the little blighters).
We have a family of green woodpeckers who nest in the orchard each year so help deal with the ant problem, although I am still considering buying an aardvark!
If I ever use soapy water I use an ecological brand that is made from plant and mineral extracts.
I guess what I'm trying to say is that I think we already absorb so many chemicals from the environment in which we live I really try not to add to it by the food that we grow and eat. If nature can help with a problem I'd rather let it than resort to a manmade spray.