None of those systems have overlapping marketshare.

WinCE is targeted at very small devices, like handhelds, GPS units, and smartphones. XP Embedded is targeted at computer-based devices used in non-computational settings for limited tasks (i.e., ATMs, arcade machines, kiosks). Vista is an upgrade to XP.

Expecting a bug-free OS from Google is a stretch. Remember Android? Google put a chunk of brainpower and marketing muscle behind that, and it's nowhere close to being bug-free...and it's already been out for a year.