We stayed at the Park Hotel initially because of it's close proximity to Tokuda Hospital. We are very pleased with our choice! The hotel was very clean, the staff extremely friendly, and the atmosphere was like a home away from home.
Our designated room was gorgeous and had a lovely bow window overlooking the courtyard. Unfortunately, we had to opt for a room with a separate shower, because the combined bath/shower was quite deep and hard to get into! We moved to another room, and although it had a bath and separate shower, due to lack of space, it was minus the bidet, which was a bit disappointing. The partial bow window was smaller, but the room was large and comfortable.
The complimentary breakfast was just short of amazing! The croissants were worth writing home about, and the bacon was rated the best my husband ever had!! There was such a wonderful choice of food ranging from eggs, fruits, yogurt, salamis, cheese, breads, cereals, potatoes, olives, various condiments and assorted toppings.
The restaurant was open for dinner and the only drawback was the menu got to be monotonous after staying six days. A suggestion would be to have a daily special of a traditional Bulgarian dish. The choice of food was strictly mainstream and although very tasty, I think when in Bulgaria, eat the local dishes!!
The hotel was away from the city centre, but a taxi could very quickly take you downtown and elsewhere at a very reasonable price. We also opted to hire a taxi to take us to the Rila Monastery, about a 2 hour drive, which was very reasonable and a good way to do some sightseeing.
We enjoyed our stay at the Park Hotel so much, we intend to return in warmer weather and continue our sightseeing

I stayed in this hotel for a seminar for more than one week. I liked this hotel a lot. The rooms were extremely comfortable and fully equipped with everything. The shampoo, soaps, cleaned towels every day. Everything was very clean.
The food was very good, but it got boring after a few days. I loved the location of the restaurant as it was so bright and in some kind of terrace that was very beautiful.
What i liked most was that it was really clean and tidy what I liked lest was the location. We walked the first day till the NDK and it took us at least 40 minutes and a quite tiring walk for me. The rest of the days I used a taxi that in Sofia are really cheap (for 2-3 Euros) so its not bad.
In overall I found this hotel very good

Hotel is quite nice, with spacious modern rooms.
Breakfast is quite basic, but in a nice sunny hall.
Complimentary internet is good.
The main minus of the hotel is its location, next to nothing but a few office buildings (and a hospital). Even for a small snack you have to get somewhere else (personally I never looked for public transportation there other than taxis, so I'm not sure there are any).
I would stay here again only if I have meetings in one of the offices next door, and only if I don't get to spend even a single evening there. Otherwise, better stay at the center, where there's more to do other than sit in the room; and you will anyway want to travel to the center an back.