Litotes is a nice trope to have in your tool bag. I always thought the Orwell was reacting against a certain type of British rhetoric when he spoke against it in his essay "Politics and the English Language." I can easily see how its overuse could become tiresome, but I don't like the idea of ruling it out completely.
Litotes is expressing a concept in the opposite way, but negated. "A considerable sum of money" becomes "A not inconsiderable sum of money." The advantage of litotes is that it allows you to express a different shade or twist of emphasis. I disagree with Orwell when he says it is obfuscatory. It doesn't conceal your meaning, but expresses your particular attitude toward the meaning. In most cases, an attitude of ironic understatement. Just as hyperbole has its uses, so does understatement. You wouldn't want to rule out any shading of attitude.
I can't say I use litotes often myself, but I consider it a not ineffective trope in the hands of a good writer.