Uncomfortable, pretentious, expensive
I visited it with a couple friends on a Friday night. We were looking for a place to have a drink and eat a bit (tapas, or a ración to share; something simple like that).
We were seated in the dining room, which was a bit too dark. The lamps hanging from the ceiling were too low, though — so the effect was that you felt the light in your face and in your eyes a bit too much. The table and chairs were not really comfortable, and there wasn't much space in the room, either. The mats are plastic mats, they felt awkward, and the dishes and glasses stuck to it a bit.
The menu was short, and, iirc, did not include desserts. All dishes seemed kind of extravagant and whimsical (weird mixture of cuisines and ingredients). We ordered just two or three things to share (ceviche, something with boletus).
The food was good and tasty, but portions were too small.
Bocacalle seems okay-ish to try a a few new things with friends, but a bit expensive. If you want to have a meal and be full, you'll have to order one or two dishes per person, and it won't be cheap.