The apartment ist very nice, a lot of space, comfortable bed, big living room, good kitchen and big bathroom. Everything was clean. It's in a huge gated apartment complex but both Cardiff City and Cardiff Bay are in walking distance (20-25 min). You can also take the bus. Mermaid quay with Tesco and Sainsbury's is a 10-minute walk. Check-in was easy, I was met by a very nice member of staff who showed me how everything worked.
One thing though: there was no dishwasher, though dishwasher tabs had been especially laid out. There was a washing machine though, but no detergent. So maybe staff confused the two?