Enrique's apartment is great. It's small, but it's well designed and comfortable. I stayed alone, but it would be adequate for a couple, especially because the patio is so spacious (essentially doubling the square footage of the apartment), and the weather is mild enough that you can use it as a living room.
The windows along the patio make the apartment pleasantly bright, and you can see Tibidabo and even glimpse La Sagrada Familia from the patio. The apartment is also reasonably quiet -- especially given that sound carries pretty far in the Gracia neighborhood. Internet was fast, too, which was great.
Other than being a little noisy, the Gracia neighborhood is great. Feels like a neighborhood, not a tourist destination. Safe, walkable, tons of great places to get a meal or a snack or a drink. Enrique's place is very well located to take advantage of the neighborhood and its eateries and markets and plazas. The apartment is also very close to the Metro, which is fast, safe, and easy to use. I really loved staying there.
My ONLY complaint is that the apartment is managed by Sweet Inn. Sweet Inn is a company based outside of Spain that manages vacation apartments in a handful of cities. I found it very frustrating trying to communicate with them by phone or e-mail. I got different information depending on whom I was communicating with. The folks at dispatch couldn't even find my reservation when I called.
That said, the people who work in Sweet Inn's office in L'Eixample are helpful and very warm. If you have concerns about your reservation, your best bet is just to go straight to the office and talk to them.