I never knit with pure acrylic. It just feels nasty and plasticky and squeaky and makes my hands hurt. It also tends to have that icky, plasticky shine. The really cheap acrylics look and feel *flammable* to me. That said, I do occasionally use acrylic blends (either with cotton or with wool); they are good for things like baby clothes that have to get washed/dried a lot. I do try to avoid buying things (both yarn and ready to wear garments) containing a large percentage (say >30%) of acrylic.
I don't really think acrylic pills more than wool, although it is true that many acrylic yarns are cheaper and thus probably not as tightly or carefully spun and knitted. The primary determinants of whether something will pill is the fiber length (merino has short fibers, hence it gets very pilly), how tightly the yarn is spun, and how tightly the yarn is knitted. Softness is unfortunately often an indicator that something will pill since it correlates with short fibers and loose spinning/knitting. (Think about woolen socks, which are made from tightly spun yarn knitted at a very tight gauge, vs. a soft merino sweater).
