We stayed in Johanna's apartment for 4 nights with our 2 girls (aged 13 and 9). We really liked the location and the space was perfect for what we needed. Might be a little small for 4x adults (on account of bunk beds) but ideal for us as a family.
Choice of location can be quite subjective, but it really felt like being in a "proper" part of Barcelona, very central but nicely away from the main crowded areas. The Metro literally a couple of minutes away and we hired bikes from Donkey Republic which can be picked up all over the city. On the occasions when we were out and about and decided to get a taxi back it never cost more than €10.
There's a nice patisserie opposite and various food shops along the road where you can get everything you need.
The apartment was clean, cosy and homely - and having Netflix was a treat.
Although there's a lift, it's a small one so be prepared to use the stairs if you don't like small spaces (it's 3 flights up).
If you want a taste of 'real' Barcelona, it would definitely be worth a stay!