This report might be useful:
My summary of sofia would be:
Negative:
- supply of 1/2 bed apartments still exceeding demand
- rental still very low (ignore the agents who tell you that you'd get 800 euro per month for a 2 bed, you'd be very luck to get half of that)
- it will be a long time before normal workers will be able to afford the apartments that are being built.
Positive:
- Lots of investment going in to sofia, major shopping malls, lots of new foreign companies e.g. a lithuanian company announced a 500 million euro shopping complex the other day
- Prices are very low compared to capital cities in places like poland
- Labour is very very cheap and corporation tax was recently reduced to 10%.