Here's my "wish list" (somewhat in priority order):
(1) Mild climate with significant sun (ability to spend most days of the year outdoors). I am fine with some winter and some summer, just not the extremes.
(2) Access to good health care and health insurance programs/exchanges.
(3) Access to the great outdoors -- for running, biking, walking, golfing
(4) Urban amenities with a smaller town feel. I do not have an inherent dislike for suburbs, especially if well connected by public transport. We don't need to live in the middle of it all, but would like access to it. Urban areas with a strong "neighborhood ethic" could be appealing.
(5) Reasonable taxes for retirees. Decent cost of living.
(6) Laid back attitude. Progressive values.
(7) Access to major airport.
I've lived in Washington and Colorado. I currently live in Eastern WA, with plans to retire to Western WA in 10 years.
#1: Western WA isn't known for it's sun, but it's mild year-round. Eastern WA has four very distinct seasons, with each lasting about four months. Winters are variable. Sometimes sub-sero temps and lots of snow, other years mild temps and a bit more sun. Just depends on whether our winter storms blow in from the Pacific or from Canada. Definitely mild compared to Midwest winters, though. Southern WA may have milder, sunnier weather, I don't know.
Colorado, on the other hand, is generally sunny and mild year-round-- at least in the Denver area.
#2: We've had good luck on the exchanges as a self-employed family. Lots of choices and large doctor networks. WA is very forward thinking when it comes to social programs. For dental, we use the local dental college. Ours is great, but I hear the one on the west side of the state is even better.
#3: The entire state is one giant outdoor playground. This is our primary motive for staying here.
#4: Lots of small towns with the urban benefits, especially as you go west. In Eastern WA, there are no true suburbs, just small towns that surround the main city. We're in Spokane. We have strong neighborhoods here -- some stronger than others -- but most have their own street fairs, festivals, parades, and block parties. A very similar feel to the different festivals in the small towns throughout Nebraska and Kansas.
#5: Cost of living is great in the east, a bit higher in the west. No state income taxes, which is a major bonus. Sales tax and property tax is slightly higher than in states with a state tax, but not horribly so. Most of our expenditures are food, which isn't taxed, so we don't really feel the sales tax.
#6: There are progressive and liberal enclaves in the east, and they are growing. We picked our neighborhood specifically because it is more progressive, but generally, Eastern WA is conservative due to the Idaho influence (but nowhere near as bad as Idaho). This is part of the reason why we plan to travel west for retirement.
#7: International airport access is available on both sides of the state, and WA is dotted with smaller regional airports so that you are never more than a short drive and flight from a hub.
Hope this helps!