I was stationed at Ft. Lewis WA (now referred to as Joint Base Lewis-McChord) for 4 years in the late 80's. It's just South of Tacoma.
The scenery is gorgeous and the Seattle area is great. You've got the ocean, the Olympics and the Cascades all within 100 miles or so. I always thought the people out there were cool, too. If you like to do things like hike, camp, fish, climb mountains, scuba drive in Puget Sound,etc., it's awesome territory.
I enjoyed it there. It rains a lot: no comparison to Wyoming or Utah. For most of the year, it rains damned near every day but it doesn't get very cold, even in the middle of Winter. Summers are really nice, though and all that rain is what makes it so beautiful out there.
This was almost 30 years ago and I didn't have a motorcycle when I lived there, so can't really comment on current traffic/riding conditions, but there would be all kinds of great places to ride when the weather cooperated. I actually really liked the area to the East of the Cascades out around Yakima and the Columbia River. The scenery throughout the entire state is just really spectacular.
Not that it's the be-all, end-all of criteria, but I would note there are very few members from that area on the KLR User's Map. If you're looking for an excellent motorcycling destination I'm not so sure because of all the rain, but overall I would rate the region highly in terms of "scenery and things to do." I still really don't know if I would want to live there permanently.