We were a group of five and stayed in the apartment for 9 days. The apartment is located perfectly, with several metro stations nearby. The Arc is only a five minutes walk, so is the Sagrada familia. The city centre (plaça Catalunya) is within walking distance. It is (max) 10 minutes if you go by metro, and a taxi fare will cost you 10euros.
The apartment was perfect for 5 to 6 persons. Two bathrooms! So no lines in front of the bathroom. The kitchen was good as well, although there weren't much pots and pans. But enough to prepare a simple meal.
We haven't met 'Michelle' but there was someone who waited for us upon arrival at the apartment who provided us with useful information. We would recommend this apartment to anyone, as it is located perfectly. But do watch out for pickpockets when you travel by metro (talking out of experience unfortunately).