I get the high performance component, but it seems most of their speed is from underlying models supporting a "diff style" edits and that a small percentage of it is from code-level text-editing optimizations and improvements.
vscode running a typescript extension (cline, gemini, cursor, etc) to achieve LLM-enhanced coding is probably the least efficient way to do it in terms of cpu usage, but the features they bring are what actually speeds up your development tasks - not the "responsiveness" of it all. It seems that we're making text editing and html rendering out to be a giant lift on the system when it's really not a huge part of the equation for most people using LLM tooling in their coding workflows.
Maybe I'm wrong but when I looked at zed last (about 2 months ago) the AI workflow was surprisingly clunky and while the editor was fast, the lack of tooling support and model selection/customization left me heading back to vscode/cline which has been getting nearly two updates per week since that time - each adding excellent new functionality.
Does responsiveness trump features and function?