Does XBMC for Windows support Blu-ray or HD DVD playback with or without menus?
Qualitatively no. There is not yet any C/C++ open source software out there yet capable of fully playing back Blu-ray or HD DVD. FFmpeg (the open source codec-suit that XBMC uses) is able to decode all audio and video codecs used in both Blu-ray and HD DVD, but, even as that might be the case, you still have to get around the DRM encryptions used by the disc formats and there is not yet any C/C++ open source software library capable of that on-the-fly, nor is there any C/C++ open source software library out there capable of displaying Blu-ray or HD DVD menus. XBMC need C/C++ open source software libraries for all of these things to fully support Blu-ray or HD DVD playback. With that said, XBMC does support .m2ts extensions, as well as the decoding and playback of all Blu-ray and HD DVD video and audio codecs. Most current audio limitations are a function of hardware related issues.