Mike was refering to handles returned by CreateFile only. It is the interface to create kernel device driver instances under Windows and consequently wineserver would need to be involved somehow. HWINDOW and such while handles too, are completely different objects and managed by independent object managers both in Windows and Wine.
A clean implementation for kernel driver support would need to support all kernel driver API interfaces through wineserver somehow, a nightmare both for performance and implementation reasons.
I've already got a (somewhat hacky) partial implementation for kernel mode drivers for copy protection drivers, so if you're interested let's try and not duplicate work, I can send what I have ATM to whoever's interested.
Ivan.