This is what I thought. After some fiddling it became clear that compatibility will be an issue for more applications than they claim.

It's probably fine for new projects though.

I’ve been thinking about this anf trying it out. The only obviously bad thing is that the ‘drop-in replacement’ is bs: they’re aiming for it but there are a bunch of node std lib modules missing. Despite that it seems to work just fine for my Expo app and RNW project.

limited Windows support -- I am surprised that this is hardly mentioned. People here may not admit this, but Windows-based developers are a huge group, and probably more than Linux or Mac (e.g. look at stackoverflow survey). If you tell people "You can't really use Bun as intended unless you use Mac or Linux or spend half an hour setting up WSL first", people are going to be turned away, especially for new developers.

It may not matter to you personally, but if it is used in a project with developers working on different platforms, it is going to present some hurdles.