Stayed between Christmas and New Year when visiting Barcelona first time. It was a good stay overall.
Pros: Great location. Nice neighborhood with excellent cafe/restaurants choices. Walking distance to many attractions. The apartment self is well decorated. Hosts are kind and responsive. The gentleman helped us check in was on-time and friendly, offered helpful tips.
Cons: Too much street noise at least from my personal preference. We do live in suburban area so people live in a city may find it trivial. Although new windows were installed, the noise can still keep one from getting to sleep or waking one up in the middle of night. None of us have sleeping problems, and fortunately we overcame the jet-lag issue before arriving Barcelona - spent 7 nights in south Spain first. Otherwise it could have been worse. After a couple nights, we got more use to it. I would say this apartment is not for everyone. After all, getting a good night of sleep is vital to a great vacation.
Other things: $50 charge for Christmas Day check in. Didn't find bath soap, paper towel or clothes detergent in the apartment.