Warren Buffett officially retired as the CEO of Berkshire Hathaway at the start of this year. He is no longer as involved in but will be the Chairman and guide the company as needed. Plus, he retains a significant stake in Berkshire Hathaway, with 38% of Class A shares being his. BRK stock is down slightly on the first day of trading, so Wall Street mostly seems content with the leadership change. Investors will now look for results and reward/punish the stock based on that.