The Device Ownership behavior (should never show the Personal flow on a Corporate hashed device, and we are not seeing support for OEMs of pre-uploading the Corporate Device Identifier) as well as Device Naming (we use asset tags that get physically added and pre-associated with hardware) have been complete showstoppers from going to Autopilot Device Preparation for us.

I have also heard others say the same about no Self-Deploy (kiosk) or White Glove, and the Application selection process is also clunky (should just be a checklist of available apps, not configuring more groups and policies).