Yes, labor is one of the things that I am concerned about, given Bloomberg's longstanding opposition to unions and resistance to labor reform, from raising the minimum wage to mandating paid sick leave.
Michael Bloomberg’s Troubling Record on Unions and Workers
Four more years of Trump will hurt, but potentially eight years of Bloomberg at the head of the Democratic Party does not necessarily strike me as a better deal. Given his record, he could very easily save us from Trump, only to put the Democratic Party squarely in the hands of big business and gut attempts at reform from the inside. Between that and the precedent that a successful campaign based around flooding social media with advertisements would set, I'm not even sure I would want him to win the general election at all, so I would stay neutral and vote third party.