Another Bulgarian here, living in London and contributing to the problem.
This is a good article, but fails to show the breadth of the topic. I also disagree with many of the comments here, which (expectedly) are on the pessimistic side. This pattern of a big spike in migrants when a country joins the EU isn't new. The Polish, the Czech, the Hungarians all experienced this. It might be frightening to project a % of the population leaving yearly far into the future, but it's almost certain that the trend will not continue. There's a trend of economic equalization which starts after a country joins the EU, and this makes it less and less attractive for people to leave over time. So although I don't see net positive migration soon, the current numbers will not be the same long.
Every time a country becomes better off, the most entrepreneurial and driven people reap the benefits first. This is already showing in the big cities in Bulgaria and some of the comments about salaries here agree. Of course it is true that the not-so-skilled haven't benefited yet, but I think this is also going to happen and the current environment will give birth to much innovation and job creation, which will permeate society and give good reasons for even the poor to stay. These processes take time and Bulgaria hasn't yet gone through the full cycle, so we can't judge it yet.
It's true that there's plenty of corruption and bad practices, but if I compare today to what was happening in '97, it's in a different league. We went from rampant hyperinflation and drain of national reserves to small racketeering. If the bar is zero corruption, that will never happen. The good thing about the economic progress from recent years is that it's driven by industries which the mafia can't control. It's no wonder that Software and IT services are such a big employer and contributor, because it's not a business with large tangible assets that can profitably fall into the hands of the wrong people. This means that corruption and mafia have less and less impact on the quality of life of the average citizen. The situation in key strategic industries (e.g. energy) is obviously very different and won't be improving quickly, but that's the case in many developed countries as well.
There are still many things which need to be improved when it comes to quality of service and administration (at least on a public level), but these are solvable problems. I have high hopes and I'm optimistic about what's coming, with an eye open to return one day. And for those who haven't visited yet, I would whole-heartedly recommend it.