Winter brings about a great amount of darkness. Not only does the sun set so early, but in Amsterdam (and Seattle) it rarely breaks through the clouds to really shine. This does not bother me so much, and I really enjoy the added peace of dark mornings and nights. When I mention that I still wake up and run starting at (or even before) six am, people are shocked, even those who are often early risers.
The darkness of the winter can be draining, and I love the long summer nights, but as the sun starts rising earlier, the roads are not quite as quiet early in the morning. Biking home from work in the dark is initially depressing, but being able to spin through the woods without dodging others and ringing the bell is quite the treat.
This year, I purchased a bike with a dynamo wheel again, and it has made this winter a blast. It takes some motivation to go out when it is so cold, but the darkness provides motivation to get out, especially as it will not last for long. Generally the world quiets down around five, but in the winter it is practically dead.
Of course, another joy of the dark is sitting in a cozy pub and reading a book while still getting to bed by ten. Alas, that joy will presumably have to be saved for next winter when the pubs are open again.
One last benefit of the dark is that finding places to take a leak is much easier!