I've been to Sofia 4 times on business in the last 18 months. Nice city, lots of great architecture. Old Roman ruins scattered around the city that was once known as Serdika. Safe, reasonably clean, inexpensive and English is widely spoken. The Sheraton is right in the centre of the city.

You may read about some political unrest there due to the outcome of recent elections. I saw nightly demonstrations outside the National Assembly which is directly across from the hotel where I was staying. I've seen larger and more aggressive demonstrations in Toronto and the rest of the city is unaffected.