We don't use them as much as I thought we would. I think they are a better tool for letter recognition than for handwriting. They are durable if you have a toddler who also wants to participate. In fact, i think I may pull them out for my 2 year old who is letter obsessed.
We also have the slate and the Stamp and See screen. The Stamp and See screen is by far the tool we use the most. If your child likes using a magnadoodle, this would probably also be popular.