The Renaissance is a fairly nice hotel, within a reasonable distance of downtown Seattle. The rooms are quite decent, although the proximity of the hotel to the highway means that road noise is hard to avoid. Try to get a room on an upper floor facing west to minimize it. Not sure if upgrades are applicable, but the Ren usually upgrades me (MR Plat) to a corner room.

One thing to note: The position of the Renaissance atop a fairly steep hill running down to the water means that walking to and from the hotel will provide a fair bit of exercise - this can be a good or a bad thing (definitely bad if you've been indulging in Seattle's mediocre nightlife). There are hotels in better positions for sightseeing - I'm at the Elliott Hyatt right now, which is a great hotel. For Marriott hotels, I believe that there is a Residence Inn close to the Hyatt, which might be a great choice - have a look on marriott.com.

Hope that helps,
-Zombie-