I LOVE SIMPLY SOFT!!
I make almost all my stuff for kids out of either that or cotton. It is soft, affordable (with great yardage) and has a pretty sheen to it.
Having used Ingrid's washable yarn of choice (Plymouth Encore) I have to agree that I like it, it's really soft and feels great to work with, but I just can't afford the 5.75/ball (altho it is worth it!!
If you have an AC Moore nearby, Red Heart started making a softer acrylic that is kind of a mix between Microspun and Simply Soft - but it's slightly more expensive with less yardage than Simply Soft.