Like many people, when I started to crochet it was primarily with worsted weight acrylic yarn. It's comparatively inexpensive, machine washable, easy to find, and comes in a great variety of colors.
While designing this afghan for the Herrschner's contest, I chose to use Red Heart Super Saver. As I have not yet mastered the math involved in figuring out exactly how much yarn I will need for this project, I found myself running to the store to get a couple of more skeins yesterday. The "no dye lot" attribute of Red Heart has saved my project this time. There is no noticeable difference between the color of the yarn I was using from my stash and the yarn I bought yesterday.
I have found that this is not always the case, however. I have found that the colors have changed over time, especially reds and yellows. There is little that is quite as frustrating as running out of yarn when you are almost done a project and not being able to match the yarn to finish the project. That is why, when purchasing yarn for a project, I always get one or two more skeins than is called for in the pattern. You can return unused skeins to most retailers, or simply add them to your stash.
I prefer Red Heart when working with 100% acrylic as it is usually tightly wound. This makes it easier to work with, as you are not as likely to "split" the yarn making your stitches. If you catch only some, but not all, of the plys of yarn, you end up with little nubs that don't belong and make the work look messy. If you don't catch the error immediately, it can be difficult to pull out as it tends to knot.
I once made a hoodie out of Caron One Pound 100% acrylic. It worked up okay, but after one wash it looked horrible. It had pilled and needed a sweater shaver to look acceptable. I've never had that problem with Red Heart. Conversely, Caron One Pound worked up well into many afghans that have had multiple washings. Perhaps it was simply a problem with that one batch, who knows?
At any rate, I highly recommend using 100% acrylic on afghans so they are easily washable. It wears well, but tends to stretch a bit. Keep this in mind if making bags or purses. I do not think it is the best option for apparel, as there are much better options out there that drape better, look better, and wear better.