The dark is a real thing. It is not just the rain. It's more the large number of overcast days plus the very short days during winter months.

Whether or not it bothers you is a different matter. As far as I can tell, it's practically a biological thing. The lack of light just gets under some people's skin while others aren't bothered by it. Ask yourself, do you find gloomy days draining: oppressive clouds looming overhead, color washed out of everything, can't go outside, cold, wet? Or do you find them energizing: turbulent sky looking different every day, you snuggly in the warm light inside, doing creative stuff on a rainy day at home, or bundling up and getting refreshed by the cool breeze and rain spray?

If you're more the former, Seattle will suck your soul out and drown it in Puget Sound. If the latter, you'll love it.

Personally, it's a great fit for me. I love the contrast in weather between the summer and winter months. When it's miserable out, I love nothing more than settling in under warm lamplight and reading or coding. I can't imagine living somewhere arid. I would dry out like a frog on a hot windshield.

If you're considering moving here, I would suggest renting for a year. If you make it a full 12 months and don't feel oppressed by the climate at all, you should be fine.