Not only is there good potential for a speed improvement, but languages built around the assumption of pervasive garbage collection tend not to have good langua

Not only is there good potential for a speed improvement, but languages built around the assumption of pervasive garbage collection tend not to have good language constructs to support manual memory management. To be fair, most languages without GCs also don't have good language constructs to support manual memory management. If you're going to make wide use of manual memory management, you should think very carefully about how the language and ecosystem you're using help or hinder your manual memory management.