I strongly recommend Casa Olivella mainly due to very kind and helpful host, perfect location (very convenient connection with main railway station but what is more important closer to most tourist attractions) and very stylish interior.
The apartment is extremely clean and spacious, equipped with a plenty of useful devices, 2 TV sets, fast Internet and very nice bathroom.
As I mentioned above, Massimo is a really good host. He provided us a comprehensive guide and a map (much better one than the ArteCard map). We visited some places he advised us and it turned out to be a perfect idea.
Hesitate no more and book Massimo's offer, it is really worth it!