Housing is expensive. In a lot of areas, it's cheaper to rent a house or apartment than to pay a mortgage on one of similar square footage, but occasionally you can find good deals.

There is a lot of theft. Not trying to scare you, but three of my friends' cars have been broken into or stolen. King County seems to break up theft rings every few months, posting online pictures of stolen property to be reclaimed.

While there are a lot of ethnic food restaurants, they are average to poor compared to ones in other metropolitan areas, and are often Americanized. So if you like authentic spicy Tamil South Indian, Indonesian, or Thai cuisine, you may be disappointed as compared to San Francisco, Houston, or Chicago. American food and sushi, however, is plentiful and good. BBQ is rare, and finding good BBQ is often a topic of casual conversation, and it becomes a big deal whenever a BBQ restaurant opens or closes.

If you have sinus problems like non-allergic rhinitis, the stagnant damp air and the lack of frequent sunshine as a disinfectant often leads to sinus infections. Having lived in three different regions (Midwest, South, and Seattle), I've had far more sinus problems in Seattle than in the other regions. Many people have told me they started having allergies only after they moved to Seattle.

As others have said, there's traffic.