The L'Eixample neighborhood is a great place to stay. There are cafes, restaurants, bars, grocery stores and 24h markets everywhere. Barcelona is a wonderful tourist city and even in a week we did not see everything. The apartment was wonderful. We were a group of 7 people across 3 generations and everyone had a place to call their own. It's easy to get a cross breeze by opening the front and back doors. The street side half is a little loud, but once you close the doors the street noise is greatly reduced. The back patio area was wonderful for meals and hanging out.
Check in was super easy, they just turn on the electronic key. Check out was also super easy. No hassles there.
The following issues did not affect our enjoyment much, but were nuisances. There were a bunch of small / medium maintenance issues - first the smoke detector starting chirping, then it turned out the A/C units didn't work, and finally one of the dishwashers wouldn't turn off. None of these was a deal breaker but gave the impression of a general lack of attention to detail. The good news is there is always someone checking the VRBO messages so they respond quickly, but they were not able fix the issues during our stay. We were OK without AC, but later in the summer when it gets really hot it would be an issue.
Overall I would definitely stay again, the neighborhood and apartment layout were great. They just need to pay attention to the maintenance list.