i use snow foam and i definately think its worth it. the point of is to loosen and/or remove as much of the grit as possible before you wash with a mitt (not a sponge!!) so that you are dragging less grit across the paint and inflicting less damage to it. if you care about your paint then regardless of the cost it is worth it. as mentioned you need a proper lance, not the one supplied with the PW. they can be bought at a number of detailing shops. you'll also need the correct fitment for your lance ie a karcher fitment. you can use hyperwash or buy a dedictaed snow foam. remember to dilute it with water in the lance - it foams just as well and you get better value from your foam. hth.