Wonderful critters! They do have personality, and if you get a TRUE pomacea bridgesi *true applesnail* they won't eat live plants. Mine eat veggies, fish food, and algae. They come to the surface to "catch" fishfood in their foot, they "play" in the current of the filter, and are just generally neat little critters. I highly recommend them. Just be aware, they can get BIG and they do poop lots, so there is a bioload issue in a smaller tank.
There's a great website on them
www.applesnail.net
Happy reading!