My husband and I just came back from our honeymoon in Spain, and I used chowhound extensively in planning so I just wanted to report!
El Escarpin: This is a tapas bar between Puerta del Sol and Opera. It had a great atmosphere - sit by the bar, the bartenders take the orders and it's bustling and loud and everyone speaks Spanish and it was just great. They specialize in cider. The prices were a little expensive (5-15 euros for tapas), but the portions are big - it's more of place to go with a group.
Maceiras: on Calle Hubertas. Also a tapas bar - very good, and a bit cheaper, although I thought the food wasn't *quite* as good. It filled up really quickly as soon as it opened (at 8:30), and we were pretty crammed in there. It was a good place to sample some tapas and hang out with locals, but the menu wasn't that big.
La Finca de Susana - we went for lunch, which had a pretty good set lunch (less than 10 euros/person). The appetizers were good, but the main entrees were just okay.
Bodegas Campos: We did the tasting menu - it was good, but I'm not quite sure it was worth it. If I had to do it again, I would've skipped BC and save the menu to do the full tasting at Cinc Sentis in Barcelona. Everything tasted really good, but I found both the atmosphere and the food a little stuffy and old fashioned. We were also totally out of place in the restaurant. Also, it's all smoking, which I'm not a huge fan of in a dining room.
Taberna Pepe de la Juderia: I just have to say, this restaurant was more expensive than I thought it should've been, and the food wasn't good enough to justify the cost.
La Cavea: this was a small tapas bar near the Archealogical museum, and I really liked it - very cheap (2-4 euros/tapas), good selection, and the food was good. They had a nice small patio, and it was just nice to sample a lot of different things - the pinchos and the solmorejo were particular good.
Nothing special here, but we loved the sizzling shrimp in garlic at La Altamira
Tokyo: okay, we were desperate for sushi. The fish was really fresh, but we didn't really get sushi, per se, it was more like fish rolled in rice, and it was way too expensive to justify it.
El Mussol: This is a charcoal grill restaurant that specializes in Catalonia cuisine - our hotel recommended it because it was cheap and close by, but we really liked it. The entrees were reasonable, 5-15 euros, and much to our delight, they had a good selection of grilled vegetables. Nothing too special, but generally consistent, good and not too expensive. Good selection of desserts as well.
Els quatre gats: total tourist trap, but a surprinsingly good set menu for lunch - 3 courses, plus wine and water, for 12 euros. They brought us a whole bottle of wine and a whole bottle of water too. The only thing is get there early or make reservations, because we got there early and it was overrun with tourists by 2pm.
Cinc Sentis: This was the food highlight of our trip. We went for lunch, and they had a 39 euro menu, pick one appetizer, one entree and one dessert. The chef also sent out two amuse bouche appetizers and an amuse bouche dessert with our coffee. The whole experience was fantastic - I very much wish we could go back and do the tasting menu. Everything was wonderful and amazingly delicious!