I'm not sure why, but I've always happened into the best Italian food in Seattle.
Had an incredible, very reasonably priced traditional Italian meal during lunch at Cafe Bengodi right in Pioneer Square:
http://www.seattleslittleitaly.com/cafe-bengodi-restaurant.html
For a nicer evening meal, there is a larger restaurant on Capitol Hill called La Spiga Osteria:
http://www.laspiga.com/ While more expensive than Cafe Bengodi, it was moderately priced overall for a handsome, very upscale dining experience. They had a great variety of plates, and it is all presented for easy sharing. They also had great salads and antipasta plates as well as a large, well-priced wine menu (by the glass or bottle).
I would highly recommend either one.
Regarding the city itself, Pike Place Market it worth a visit. I tend to like Granville Island better, but the setting of Pike Place is nice. The downtown is pretty impressive. We actually had a lot of fun one day just visiting the main Library downtown, which is architecturally interesting:
http://seattletimes.nwsource.com/news/local/library/photogalleries/spl1.html.
I actually found Pioneer Square a bit shabbier than other parts of downtown . . . reminds me of the main touristy strip at the start of Gastown. Capitol Hill is nice for a visit, but if you are only going to be there a day or two, I'd start out by exploring the downtown.
I'm not an expert at Seattle by any means, but those were my impressions. I'd like to explore it more sometime myself.