We visited Barcelona in April, and as we were staying for 8 nights, we rented an apartment instead of a hotel. We really lucked out--what a great experience!
It's in a nice neighborhood, very close to the Metro and lots of restaurants, shops and markets. The owners, Joan & Elizabeth, were lovely to work with from the very first inquiry to the checkout procedure, it was flawless.
Here's the link: http://www.vrbo.com/291453
Although this is a link to their VRBO listing, I've left a review on TripAdvisor also
Feel free to message me if you have any questions!