Worn & Weary - Both in Appearance and Service
Pros: On the cheap side. Free shuttle service. Located a stone's throw from Seatac Airport. 
Cons: Extremely worn property. Heating/Cooling units in rooms smell of mold & mildew. Inconsistent service.
The Clarion Hotel Seattle Airport has seen better days. It is an extremely worn out property that lacks consistent maintenance and housekeeping (e.g. peeling paint, holes in walls, broken furniture, etc.). Having said that, it is also on the cheap side, so the old adage that "you get what you pay for" rings true here. Now, I've stayed in several different rooms on the property, including the suites. Unfortunately, everywhere you go there is a musty smell permeating. This is just one of those properties that has you thinking "ewww" everywhere you go. 
To make matters worse, the customer service here seems as tired and apathetic as the building. In fairness, it appears that the front desk is woefully short staffed for the amount of traffic they get from airport patrons. In the several trips I've made to this property, it appears there is only one employee per shift for check-ins, reservations, wake-up calls, phone lines and customer requests.
The bottom line is that if you only need to spend one night near the airport, this hotel is tolerable. However, with numerous other hotels lining International Blvd., there are certainly better options out there.