Just wrapped up a long weekend stay here. All around, a really nice place. We stayed at the Westin Grand about a year ago. The room at the Grand was nicer, but I think the Bayshore wins on most other points. As others have mentioned, location is fantastic as is the breakfast buffet. Full spread with no upcharge for hot items. Kids under 5 are free, but we weren't charged for our 5 year old (we declared her age and were told it was close enough). The staff, from check-in to valet, to the restaurant are about the nicest people you could imagine.
Didn't get an upgrade, but the hotel was full as there was an Amway conference in town. The egg chef, who was pretty fantastic, also mentioned that the Calgary Flames were staying prior to their game with the Canucks Saturday night.
Would definitely choose this property again! I need to work on plane tickets to YVR instead of SEA next time. The drive always takes longer than I think it should...