We stayed at Alejandro's beautiful loft in Gracia when we moved to Barcelona and needed somewhere to spend a few weeks while looking for a long term rental apartment. The loft is beautiful, the location is perfect if you want to be in Gracia but also have access to the main street of Diagonal, and Alejandro was a wonderful host.
No place is ever perfect, so here are some things to keep in mind for booking this space:

1) There is no elevator and the loft is on the 3rd/4th floor with narrow stairs. So, if you don't travel light, or if you have any physical disabilities, this is something to keep in mind.
2) We arrived during a cold patch of weather in Barcelona in November, and the heating in this loft is not great. There is a heater in the main living area but I'm not sure that it works well, as it's positioned at the top of the high ceiling, so the warm air rises and didn't keep us warm.
3) If you are a light sleeper that goes to bed early, this may not be the best place for you. There are garbage bins that get emptied by the city every night around 1am. This happens on the street below the bedroom window and there isn't good sound proofing in this loft, so it woke us up every night.