Dark energy is incredibly strange, but actually it makes sense to me that it went unnoticed, because dark energy has no effect on daily life, or even inside our solar system.
You could not have predicted the amazing discoveries at Pluto, even though we have been to a couple of objects in the solar system that were at least a little analogous to Pluto.
Pluto is showing us a diversity of landforms and complexity of processes that rival anything we've seen in the solar system.
We really just didn't realize the diversity of planetary types in our solar system. Pluto looked like a misfit because it was the only one we saw. And just as a Chihuahua is still a dog, these ice dwarfs are still planetary bodies. They're large enough to make themselves round by self gravity, and they surely pass the test of planethood.
New Horizons isn't just visiting Pluto; it's visiting this entire region. Whatever it finds, this will be a signal moment for planetary exploration - the capstone to our first reconnaissance of the planets of our solar system.
Going to the Kuiper Belt is like an archaeological dig into the history of the solar system.
Discovering that our solar system has many more planets than we ever expected, and that most of them are ice dwarfs rather than like Earth and the other rocky terrestrials, is just another step in the revolution in viewpoint that removed the Earth from the center of the physical universe and makes Earth all the more special.