Casp-er is a very good pension-style hotel in Barcelona, located in a residential, quiet street (in a gorgeous area; very close to all public transportation, markets, and places to eat and drink; walkable to major attractions). Not conspicuous, it is a bit hard to find, so use Google Maps or similar.
Check-in was a breeze; attendant was courteous and welcoming, and offered help and advice. Common areas are very small and sparse (as pensions usually are) but well decorated and clean.
The room and bathroom were very small, but adequate and clean for a couple. WiFi worked perfectly. There were two exterior windows in our room. Travel light - no closet, and the only space for our carry-on luggage was the desk. On the good side, they have a strict rule that no noise can be made by guests after 10pm, which was great (my wife is a light sleeper), and there was absolutely no exterior noise in our room. On the bad side, the structure itself was somewhat noisy throughout the night (e.g. there were a series of pumps(?) that went on at various times - not good for my wife), but it should not be a problem for deep sleepers or party-ers.
Check-out was very easy as well (they even printed boarding passes for us).
We spent three nights here and were pleased by the service and facilities. Recommended!