Version:            (using KDE 4.0.0)
Installed from:    MS Windows Binaries
OS:                MS Windows

Dock widgets are not styled correctly, it still looks like Windows 95.
I think you'll want to use WP_SMALLRESTOREBUTTON and WP_SMALLCLOSEBUTTON which have the RBS_DISABLED, RBS_HOT, RBS_NORMAL and RBS_PUSHED states. Or perhaps EBP_HEADERCLOSE with the EBHC_HOT, EBHC_NORMAL and EBHC_PRESSED states, but I don't know how well that would harmonize with WP_SMALLRESTOREBUTTON, a replacement for which is not available among the EBP_* parts.
I'm not sure what to use for the title of a dock as a whole. Windows Explorer uses the rebar background, but that's probably just the underlying rebar so I don't know how correct that is; it appears the programmers of the various Explorer bars didn't think of styling either. Perhaps EBP_HEADERBACKGROUND is meant for things like this.
For the background, I think it would be natural to have a normal rebar background, at least while docked, since conceptually a dock is toolbar-like.