An absolute must! The apartment was perfect for 3 adults and a 3 yo. The terraces are spectacular! It was such a treat to be able to wake up and enjoy some time outside on our very own private terrace. While we didn't use it much, the second level terrace has lounge chairs and an outdoor shower in addition to a great view of the city. We were there during Le Marche weekend and we caught a fireworks show from the top terrace.
The apartment building was a great location! Just blocks from Passeig de Gracia and really, lots of restaurant options every where you turned! We really enjoyed Francesco's cafe, just a block away, for a coissant and cafe every morning. Dela Crema was a cute gelateria just a few blocks away as well.
A couple of things to keep in mind. The elevator is very small. It's a tight fit with 3 people. Our 4th person often took the stairs. There are a lot of stairs to get to this 6th floor. There is a coffee machine but it's for Nespresso and Keurig capsules only. Some of the cafes do sell the pods. The stove is a conduction stove so if you're not use to using that, ask how it works when you check in.
I will recommend this apartment to anyone staying in Barcelona!