There are so many misconceptions about Seattle out there. To start, it doesn't really rain that much here. Especially compared to many other states. There may be a frequent cloud cover, which can lead to the impression that it rains a lot, but it's really just a myth.
That leads me to the other issue: Seasonal Affectiveness Disorder. Yes, people may get depressed here because of the constant gray, but let me tell you my experience: I lived in WA until I was 25. I hated it here. I wasn't happy with my life, and I directed a good portion of that hate to the state itself, and to the weather. I moved away, and came back after 5 years.
I've loved it ever since! I've been back since 2007, and all of my hatred is gone. I've made great friends in addition to the ones I already had, and the weather doesn't bother me. I truly love it here.
I will say this: it is definitely difficult to make new friends, unless you either know someone who can introduce you to everyone else, or you have something in common with the people you are trying to talk to (outside of being gay). But once you get into one circle, you can easily get introduced to other circles and build your own.
Do it. Move here. I don't think you'd regret it. Washington is a beautiful state, and Seattle is a city with a lot of character. It's very gay friendly.
Oh, and about the coffee fame: go to the small-time coffee shops instead of Starbucks, Seattle's Best Coffee (which is really owned by Starbucks) and Tully's. You'll find the smaller cafes have better coffee!