Berkshire Hathaway has long been Warren Buffett's investment vehicle, but that's about to change. Berkshire Hathaway's (BRK.A -0.33%) (BRK.B -0.56%) long-term performance is nothing short of incredible. Indeed, Chief Executive Officer Warren Buffett's guidance has resulted in shocking outperformance of the S&P 500 index (^GSPC -0.37%). Buffett is the reason that most investors look to buy Berkshire Hathaway stock. And it's now one of several issues that need close watching if you are looking at Berkshire Ha ...