The artificial stuff is really painful if you fall on it, and I ruined about 5 pairs of pants and a number of jerseys on the stuff (not to mention the foot long abrasions on my hips and shoulders) before I learned to ski on it properly . Snow is a lot easier. The only trouble with the indoor slopes is they're usually too short and too shallow to have any real fun on them, but they are a good training resource for beginners, and a useful place to practice technique if you haven't had planks on your feet for a while.