I used to use Warm and Natural, but find that the drape of it is more stiff than other options, so I don't use it anymore.
My all-time favorite batting is Mountain Mist Blue Ribbon 100% cotton, which is becoming more and more difficult to find. It produces a flatter quilt that is very soft. You *cannot* preshrink this one; it will come apart in water. Plus it requires closer quilting than many battings -- every 2 inches. I find it is really worth it for soft baby quilts.
I like Hobbs 80/20 a lot for large quilts (twin size and bigger), but have gone off it for baby quilts. I just finished two small quilts, one with Mountain Mist and one with the Hobbs, and the MM quilt is nicer. The Hobbs distorted more in the wash, with the result that the edges are a little wavy instead of flat, plus it is not as soft as the Mountain Mist.
I have some Hobbs wool batting, but haven't tried it yet. Other battings I really want to try are Quilter's Dream request and select cotton (especially for crib quilts), and Hobbs polydown. I have always preferred cotton batting to poly, but I have heard some good things about the polydown -- faster to dry for kids' quilts, and very durable -- so I would like to try it.
I never preshrink batting, as I like the crinkled look that comes with cotton. Poly doesn't shrink, so there's no use in prewashing it.