Somewhat late, as this is a short roundup from my trip to Vitoria-Gasteiz from summer 2010. Searching around Chowhound yielded nothing before I left, and it remains that way. Spent more than two weeks there, so here are some short reviews:
The four places I really liked were Toloño (Cuesta de San Francisco, 3), La Malquerida (Calle Correría, 10), Saburdi (Calle de Eduardo Dato, 32) and Sidreria Sagartoki (Calle del Prado, 18). All are excellent. If you're short on time, I'd recommend them in that order, but that's quibbling. Sagartoki perhaps leans a bit too more towards artsy/whimsical than I'd prefer. Did try a couple of others that were not quite at this same level, but it did seem in general that the level of cooking was high.
Asador Sagartoki: had a fantastic ribeye steak. Came with a small portion of fries. They also recommended a rioja (2001 Viña Alberdi) that was outstanding. Not cheap by any stretch, but I'd definitely return.
Wanted to try but didn't: Arkupe, Restaurante Matxete.
Here's a helpful site for Vitoria restaurants: http://ondoloinapartments.wordpress.com/
We did a lot of cooking while we were there. The (indoor) market at Plaza de Abastos (a few blocks SE of the central part of the city) is an amazing place to shop and, I believe open every day except Sundays (not 100% sure about that, though). There are numerous stands for meat, seafood, produce, cheese/cured meat, bakery and whatever else you need. The quality was uniformly high, except perhaps the produce was a bit limited in selection, but I live in California and am spoiled. On some days (I can't remember which - but you can ask at the main tourist office) there is an open market in the open area in front of the main market building, and the vegetables and fruit seemed a bit better there.
The wine store Oleo Gourmet (half a block from Toloño on the same street, beside Ortopedia Fariña) was our favorite wine store. They let us try a whole bunch of different wines for free before deciding. They were also really knowledgeable, friendly, and put up with my mediocre Spanish with a smile.
Overall impressions (off topic): While not on the main tourist track, I thought it was a really fun place to hang out. Far less touristy than either Bilbao or San Sebastian, and perhaps as a result, the locals are very friendly towards visitors. It's also a great place to be based as lots of sights are within an hour's drive. We definitely did not exhaust the possibilities in this area, despite spending 2+ weeks there.