The flat is reasonably big for 6 (pull out sofa bed in the sittingroom+ 2 single beds in one bedroom & 1 double bed with a very bouncy mattress in the ensuite bedroom).
The flat is beautifully situated: 5 or 10 min walking time to the beach and approx. 10 or 15 min walking time from metro line (n4) and tram line (l4). It's easy to get around. There are food shops, pharmacies and lots of little restaurants all around.
The street is very calm and we slept well (we went in November - practically no one in the streets from 9 pm onwards).
Make sure you book for attractions before you go to the Sagrada Familia, parc Guel etc. Even in November these places fill up quickly!
The kitchen is designed for 4 people and the pots, pans, microwave oven, etc. are a bit small to cook for 6. The fridge and freezer are very big though. The water in Barcelona tastes horrible. They have a filter for the water in the flat. You can also buy bottled water of course.
The flat is reasonably well equipped. When we went there was a coffee machine (using capsules), a kettle, a mini microwave oven, a medium sized oven, pots, pans, a frying pan, a dishwasher and a washing machine (no dryer), etc.
Go out and try the delicious tapas!
If you come by car, you are limited to 2 hours parking time in the front of the flat. You will need to find alternative parking space somewhere else (either a car park or a street that allows free longer parking time) to park longer. We found a covered car park abound 10 min away and it added about 60 euros to our budget for 5 days.
Enjoy your stay!