We stopped using softeners about 4 or so years ago, not long after we got our Samsung TL, when my mom's aunt told us about the oils and fats in them and what they do to your machine (she had an almost 20 year old LG TL that was depositing black flakes into her loads, and when she phoned LG she was told its from softeners, so she cleaned her machine out with hot water and dishwasher powder, and stopped using softeners and no more problems).
So when we stopped I also ran a hot wash with dishwasher detergent, and we didn't even replace the softener with vinegar, so there's no additives in the rinses at all and most of our washing is line dried (perks of living in SA) and we've noticed no difference in the softness of our clothes, but we have noticed that everything seems to dry quicker. And we iron nothing, so I can't commment on the ironing benefits. Heavily wrinkled things get tumble dried so no need for ironing.
I don't add anything to my rinses either in my LG FL, just white vinegar in the softener dispenser with my weeks gym clothe.
Here in SA many people actually keep a fabric softener refill sachet in their cars under a seat instead of buying one of those car fragrance things. Very clever. As it never needs replacing. Think I might just do that too
