Sol's place is really great. It has a modern feel, and it was really clean. The location is fantastic. Anything you'll need is within walking distance. There was more than enough space for the four of us staying there.
There was a little street noise in the evenings, but it was less than I expected given how close the place is to great nightlife.
The only thing we didn't like is that one of the showers wasn't working for most of our stay, but this seemed like an incredibly rare occurrence. I think we just got unlucky.
Overall, we can't recommend Sol's place enough; we really enjoyed our time in Madrid!