I guess that the problem is caused by WinDbg using MASM syntax parser by default, and VisualDDK using C++ parser (switching it every time would be very slow). You can try using @@masm(nt!…), however, in the future versions, I’ll add automatic redirection to Disassembly window when the ‘u’ command is typed.
Regarding the automatic command completion by ‘TAB’, is there any textfile, containing a list of all WinDbg commands? Parsing help files and rebuilding it could be quite inaccurate. If not, I’ll maybe add this support to next version, but provide only a sample command list file, encouraging users to update it.