I'll start with the good. Pension Iturrizza is in a superb location in San Sebastian's Old Town. It's on a quiet side street near a church, very close to excellent dining (which is everywhere) and steps from the dock, beach and aquarium. It's hard to imagine finding something so convenient for what is a very good price. If all you want is a place to drop your bags and have a place to sleep, go for it. You probably won't be disappointed.
Unfortunately, I can't give more than three stars for two reason. Most importantly, there was a terrible odor in the bathroom that didn't go away. We only saw a staff member once during our entire stay, and while he was very friendly, we were on our way out and didn't bring it up. Secondly, our room was unbelievably small. It's almost hard to walk around the bed. There's a tiny closet, but mostly we had to step over our belongings on the way to the bathroom. Other reviews mentioned the small size, but we weren't prepared for just how small it was.
The reviews and listing also make it seem like there is a patio and/or outside space, which we never found. There was a small window in the room, but it looked out over an interior space which was really just a column of dank air looking at other interior windows.
If you've gotten this far, I'll say we probably wouldn't stay here again, but if you don't care about space or a view, you'll probably be OK with it. I assume they'll take care of the smell in the bathroom.