We enjoyed our stay in U-Nique Barcelona. Communication especially is very good and works anytime during the day. The apartment is simply great. The area is also a nice one and calm. We would recommend it also for families with kids.
However, we had two small issues: apartment has all equipments you need, however please take care not to use several ones at the same time since electricity might simply go off (seems due to a load / a limit of kWh!)
Note also the fact that elevator doors are very narrow (our twin stroller is 78cm and was not going in, due to which fact we had to unfold and fold it several times during the day).