We had a lovely stay at Lino + Guille's. The apartment is great, tasteful and spacious. They take hosting to the next level and really see to it that your stay is perfect. They've even made their own guide to Barcelona and also provide other guides. Check-in and check-out were effortless.
In Barcelona it's rare to get 'real' heating in apartments, so this was a HUGE plus for us (it gets pretty chilly in January).
We've been to Barcelona before, but never to Poble Sec. It's a charming neighbourhood and has a very local feel to it. I would imagine that during high-season it's really nice to get away from the masses and try to blend in with the locals.