I love a card like Desperate Ravings because its value isn't immediately apparent. It's sort of like Balance in that you need to play it a little bit to see just how good it can be. Here's the fundamental bit about the random discard: it's not as random as it seems. It was inspiring to listen to Patrick Chapin talk about the card in the Worlds Deck Tech video this past weekend. He said basically that you cast it if you need lands, you cast it if you need spells, and if you don't need lands or spells, you don't even need to cast it!
When you decide to cast Ravings, you're looking at the rest of your hand. You know whether you'd be fine trading any one of those cards for two more. You've made the choice, even if it's "I could lose three of these four." Your chances of losing that card are one in six by the time you've cast the spell - incredible! I think more people will adopt Desperate Ravings when they play with it more; the in-game feeling of looking at your hand and deciding that you can go +2 cards on what you're looking at is informative in the way that mathematical explanations often fall short.