We bought off the lot and it had the deck option already...so no real choice.
We've only used it a couple of times but currently we are traveling by ourselves. For the most part, if we want to sit outside, we just put chairs out on the ground. I suppose if the site was muddy but no rain, it could be handy but so far, hasn't come up.
Come spring when we get back to Michigan, the situation may change.
We have friends with the side deck and they have it out all the time. They rarely are sitting on it but it's great when a group gets together for dinner. It basically gets used as a big buffet setup to put out all the food. Or when not being used for food, they let the dog hang out on it (rails up). Let's him be outside without messing about with leashes.