This apartment is PERFECTLY placed. It's minutes from the Metro at Diagonal, which can take you anywhere. The street is absolutely charming and even though it's in a hip and lively neighborhood, the apartment was perfectly quiet. Be sure to go RIGHT out the front door and walk up into Gracia proper -- it's a fantastic neighbor. There's a great grocery store just a 3 minute walk away, and some really good restaurants within blocks.
Also, as a side-note, the apartment has a full-sized refrigerator! We've traveled all over the world, and you don't see a lot of those outside the US. That was a nice surprise.
We had some minor issues, but the host was a great communicator, and we had a very comfortable stay.