It's a controversial decision, and many people like it, but I'm probably a conservative. I think there is no need to mix styles and trends of architecture in favor of the so-called "modern art" (in a broad sense), especially on objects of architecture and history of global importance. I don't like. Although it was funny to look through the glass of this pyramid down into the bowels of the museum.
It's beautiful, but there are always long queues at the entrance. It's easier to go through the subway, buy tickets on the website and visit the Louvre, and then see the cube from below. There's not much difference, but you won't be queuing for at least an hour and a half.
Here is one of the entrances to the Louvre. Despite the crowds who want to get to the museum, the passage through the pyramid is very fast. There are signs with the time of entry. Very convenient. It's your time to get in line. The dome itself is nothing special.