I did it once before. You really need to saturate the peat before capping, otherwise you get a lot of air bubbles in the peat layer. Also, you should sift if it you plan on using peat from those large bales sold at big box stores and garden centers. Some bales are loaded with sticks. Otherwise, it's a great nutrient sponge and will release tannins if you like the look. Eventually it will break down into a nice loamy dirt layer.
The Fraternity of Dirt #112