I did this because there is no digging in my rock solid ground. Did not cover the holes but use them for herbs and annuals. I also lined with weed barrier cloth and used rebar in several places for stability. I love it and makes maintenence super easy.
Here's a solution to the ongoing problem of having to drag hoses and sprinklers around your garden beds: Aquacorner, an instant tap for your raised garden bed. Pair it with a soaker hose that stays put as your harvest grows.