How is their emacs keymap support? I tried VSCode for a while but switched back to emacs because it was so slow and the keymap was not very good. I've been intending to try Zed but emacs is working well enough so the motivation isn't really there yet..

I've got emacs keybinds in my muscle memory and Zed works well for me, although there's no kill ring and the macro system is nothing like emacs. The former will be added at some point (there's an open PR), but I do not expect the latter will ever be comparable.