The "Chromium-like user interface where tabs can be torn off and moved between windows" would be awesome if it were implemented directly in Mac OSX. Then applications could drop all of that code and just let the OS deal with it. Also, you'd be able to group distinct applications. I'd love to have a [Browser, Text Editor, Terminal] tab group.
EDIT: Another thought... Chrome tabs don't look like any other tabs in Mac OSX. Applications lose uniformity as they're forced to define more about themselves.