I stayed in the Petite Penthouse for 35 days and I have to say I really enjoyed the place. It is small, maybe a little more so than it appeared in the photos. But it is cozy, intimate, and all around great. I was there by myself but would have been a wonderful place for a couple. The small terrace was great for morning coffee and the rooftop terrace is the single best part of the place. The views are incredible. You can literally see every important building of interest in the old part of town from there. Its also fairly secluded, so its great for relaxing or sharing time with friends.
The apartment was well equipped with pretty much every convenience, washer/dryer, dishwasher, fridge/freezer, everything you'd need. The location also couldn't be better. Its a lively neighborhood with great restaurants and is near just about everything. By metro, train or taxi you can be anywhere in Barcelona in little to no time. Very walkable to the central train station (10 minutes) if you want to do any regional travel or simply to take the train to the airport.
I think the Petite Penthouse is perfect for business or leisure travelers. I was there more than a month working from the flat (which has great wi-fi BTW, which is a luxury in Spain) with no trouble. But for work, play, weekend romance or long-term crash pad this place would be perfect.
My only caveat, and take it with a grain of salt because I'm mostly joking is the stairs. The building is very old, clean, but old. As such there is no lift. There are 100-something stairs to the flat so its a bit of a workout. Word to the wise, pack light! Getting my bags to and from the flat was definitely a struggle and just coming home at night after a handful of mojitos can be challenging. But after 35 days my calves are rock hard and my ass looks fabulous so totally worth it! Just be aware. That said, don't let it sway your choice. The place is great and the pleasure is worth the pain.
Finally, and maybe most importantly the host and his helpers were an absolute joy to work with as well. They were super accommodating and happy to help. You will for sure enjoy your stay in the Petite Penthouse. Great place to stay in sunny BCN.