Interesting article, and worth the read. Cheerfulness plays a large role in Nietzsche's alternatives to 19th C German pessimism. It's an uncanny, eerie cheerfulness, though. You can see the seeds of post-modernity in lines from Nietzsche like this:

"I love the magnificent exuberance of a young beast of prey that plays gracefully and, as it plays, dismembers."

It is as though Nietzsche is saying, "Hume was right about cheerfulness, but the future will be challenging. We will need a new species of cheerfulness, that may not resemble that with which we have thus far been familiar."