Would you trust a vendor preinstall of a desktop linux distro? Standard practice for Windows power users is to put down a clean install of the OS over whatever the vendor preinstalled, for power users I'd be happy with doing this for GNU/Linux distros even when the system comes with some flavour of Linux-based OS.
ChromeOS provides a set-and-forget OS that avoids the Microsoft tax and works for the non-power-user. As long as there's a supported method of reinstalling an unsigned OS (previous iterations of Chromebook have had this, but it's always something to watch for), that should be suitable for the power user to reinstall over.
In the magical future when there's big commercial support for users on desktop GNU/Linux, then it will be important for vendors to preinstall a desktop-grade OS, but not now. ChromeOS devices should become cheaper and cheaper, not more and more powerful for the same price.