The warranty on your HE washer almost certainly says you must use detergent made specifically for HE washers. You have to weigh the risks and make your own decision.
Having said that, I use homemade powdered detergent in my HE washer without any problems. It is low or no-suds. I grate a bar of Kirk's castile soap and add two cups of that to one cup of washing soda and one cup of 20 mule team borax. I use one tablespoon for a small to medium load, more for larger or dirty loads. I like it because its cheap, works extremely well and it doesn't irritate the sensitive skin of my family.