Nice, big place on the far back edge of Gros (in relation to the old town) -- you will have to do some walking here: I believe it's a mile / 1.7km to the tourist office at the foot of the old town and to enter the old town, the port and La Concha, etc. are of course further still. Gros is cool and for me perhaps more pleasant to just hang out, though. (Zurriola Beach is also really nice, just not amazingly huge and beautiful like La Concha.) The value proposition of this place is based on geography so decide what your priorities are.
Plenty comfortable place, though the 3rd sleeping area is a loft / crow's nest a staircase above the living room. The issue for us was ventilation -- the back bedroom has none and in the others there is the choice between train and traffic noise when the windows are open and stuffiness / heat when they are not. The standing fans that are there do a good job, and when temperatures are cooler this is probably not an issue at all. (Note: one fan was problematic and our host replaced it within a couple hours.)
2nd bathroom is tiny but nice to have with groups and the shower worked well.