Cathy's apartment is wonderfully located, especially if you're going to the Convention Center. It's near enough to downtown and all that it has to offer and is also within walking distance of the market. It's not too far from LINK, either (though I recommend the Westlake Station, not the one at Seneca if you don't want to pull your suitcase up a hill).
The apartment itself was lovely and clean. There's a European-style washer/dryer if you need it, and even an aromatherapy diffuser to calm down after a long day. Cathy has also put together a binder that has a number of suggestions for dining and drinks and things to see.
Check-in and check-out was a breeze and the location felt safe and secure. Overall, it was a great place to stay while in Seattle.