Great budget-friendly apartment! It's a small studio, great for short stays. Easy to walk to nearby beaches, the walk downtown is a bit longer (about 30 minutes), but there are bus stops a few steps away if you prefer it.
The building is a bit old, but nonetheless the apartment has a modern look, it's nicely decorated and it was very clean. There's a pretty nice view out the windows.
I warn tall people that the bed may trouble you a bit, my boyfriend's feet hung over the frame, I had no problems at all. It's possible that the sofa bed underneath may have been a better option, but we didn't try it as the mattress on top was very comfortable and we preferred it over the sofa...
Traffic can be a bit loud on the street, but it was very quiet at night. Wifi worked very well.
Overall, had a very nice stay, Biarritz is really beautiful and the apartment was great for what I needed.