1. It's generally janky whenever the language server is slow, in ways that Neovim is not. The most visible one of these is that completion does not take into account the characters that were typed between when the completion request started and when the completion was selected. For example, if I type "abc", and the LSP suggests "abcdef" after having only observed the "a" keystroke, Helix will end up with "abcdefbc" as the final output. This is annoying.
2. The posted directions (https://github.com/helix-editor/helix/wiki/External-binary-f...) for configuring prettier didn't work, there are no error messages visible in any logs. I haven't had the bandwidth to dig into this yet.
3. Helix doesn't detect the correct root for my language servers in my environment, and it doesn't seem to have any way to override the detected root. This means that have to start the editor in the directory that I intend to use as the root. This gets really problematic when I'm working across several languages.