I can never quite figure out why I listen to it so rarely. It's more than deserving.
Like much of his music, it's huge and unwieldy and often bombastic. Yet like so much of his music, those facts are mostly features, not bugs. There's a shocking amount of joy and energy in this piece, and it has never struck me as particularly "solemn." I especially love the shouting that takes place during the Resurexit. He can think of no better musical way of expressing Humanity's excitement at what is taking place than by just belting it out, melody-free.
The Gloria's pretty crazy, as well.
Here are a couple of versions for your Sunday listening pleasure.