Penny asked yesterday what the Sirdar Supersoft Aran was like to knit with, as she has a pattern that uses it. I should qualify my post by saying I used Sirdar Supersoft Toddler Aran, I'm not sure if they make some that's just Aran!
It's 100% acrylic - I know there's a lot of knitters out there where that would be enough to put them off rightaway! When you're knitting stuff for wee ones though it's ideal as it can be chucked in the machine and not worried about.
It knits really well and keeps it's shape - the cabling I did on the baby blanket is really well defined. I wouldn't say it's the softest acrylic I've knitted with, even though it claims to be 'Supersoft'. I made a hat a while back in the same yarn but it was in grey and blue, and my memory of that yarn is that it was much softer once knitted.