Initially you just didn't get Settings Sync as it uses a Microsoft account and you had to use a different extensions gallery (but the MS one still lets you down

Initially you just didn't get Settings Sync as it uses a Microsoft account and you had to use a different extensions gallery (but the MS one still lets you download extensions as a file to install into Codium). Nowadays you also lose Remote Development, Codespaces, Pylance, some C# features, and various other MS authored extensions.