This was a great apartment. I was there for the Bulgaria v England football but went for six days, wanting to see the city and surroundings, and this was ideal, right by the main pedestrian street and the park in front of the palace of culture. I had a balcony (shared), which was great as I had hurt my left foot just before travelling so could relax when I wanted to, but the sights were a short distance away. The apartments are high above street level - 5th floor and up, I think - so are quiet but there's a dedicated lift. My apartment was clean and well-equipped. Cable TV gave me BBC World, CNN and Eurosport.
One tip - however you book, visit the website, make contact that way and get their mobile number. It's apartments not a straightforward hotel, so while they're very helpful they're not always on site.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC