We really loved the location of Sofia Inn Residence - it's right next to the main shopping street and convenient for transport as well. It can be hard to find but the owner has put up a sign so it's not so bad. We were met by a friendly lady who showed us our place - it was the top-story studio and the views were great all around. We stayed for a week so only got service (linen and towel change) once - the towels did get stinky so we would've preferred a more frequent towel change but I suppose we could've asked. This is a budget place so that was expected.
Security is pretty good - you use your keyholder to buzz into the building and operate the lift. The room was pretty basic and needed refurbishment but suited our needs. There was a stove top with 2 electric burners, a microwave and an electric kettle, as well as pots/pans/plates/cutlery. Like a previous reviewer, I wished that they would've stocked up on salt - the salt shaker was empty.
Since we'd asked for twin beds, the hotel brought in a daybed in addition to the main bed, which was really uncomfortable. The main bed (american full size, british queen size) was ok. The blinds were too light to darken the room to any significant level. In addition, the noise off the street was preventing us from sleeping so sleep quality was fairly poor. The place was more or less clean (tiled floors all around) but the leather couch was seriously torn and more or less gutted and the furniture was old. The toilet was a wet room so take care not to spray the toilet paper roll when showering! There was a hole in the wall behind the toilet, which was covered with some posters. There was no lid on the toilet. I suppose you could call it "student dormitory level" accommodation. The TV worked fine and had some english speaking channels (I speak bulgarian so i was fine). There was also free wireless internet, which worked well. Outside there was a sitting area with some chairs (behind the building), which we didn't use but it looked fine.
Finally, there was some noise from the neighbours next door (someone talked on the phone for about 2 hours) but the street noise covered up most of that!
No one bothered us for most of our stay and it was good to have a kitchen and a convenient central place to stay, so overall I rated it a "4". If you are really worried about sleep quality and mind the student-y furnishings, don't stay there. Otherwise, the serviced apartment thing a great idea and if the owner refurbishes it and puts in triple glazing, it would be perfect.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC