I've been using wool batting on all of the baby quilts that I've been doing. I don't do any thing special to it in terms of washing. I wash it like any other quilt. In fact, right now my son is using a quilt with a wool batting. He is 3 and while he uses the toilet 100% of the time during the day, he still has accidents at night and sometimes during nap time. So that quilt is washed A LOT. I've had no shrinking, bearding or any other problems with the wool.
I like wool batting for many reasons but one big benefit is that the burn resistance is superior to any of the other batting materials. I do not like the idea of using anything with fire retardant chemicals on anything that a baby uses. I just don't believe the chemicals are safe for anyone let alone developing babies. I wash all of the children's bedding and pajamas with the strongest regular detergent that I have to remove as much of those chemicals as possible.
Also, wool breathes better and helps to regulate the temperature nicely and is lightweight. I know that some people may bring up the issue of wool allergies but that is not usually an issue with high quality commerically prepared battings. People that react to wool are primarily reacting to lanolin left in the wool or the chemicals that are used in the processing of the wool.
Also, with the wool batting, it has a nice loft when quilted yet remains light and fluffy. I use Hobbs wool and Dream wool. I like them both.