To start I am using Windows Vista on my notebook and I have it setup as an HTPC for my 50" TV.
DVD Playback - I have noticed from time to time interlacing, but for the most part everything works great. I do watch all of this through Media Center though.
DVD - Playback The default MS codec seems to work very well for me.
Codec issues for Divx and Xvid - ffdshow
How to play DVD rips -
Registry key - HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Media Center\Settings\DvdSettings
Registry value - ShowGallery
Registry value data type - REG_SZ
Registry value data - Gallery = enable My DVDs; Play = do not enable My DVDs
Open With - I still have it when I right click on a file.
Power Settings - Yeah, I am not a fan of new power settings, yet.
Minor hardware changes - I havent seen any issues yet. I am using Standard Dell machines with just a few hardware changes. Maybe minor is a relative term?
Media Center and media issues - I recommend going to
http://thegreenbutton.com. I have been able to make a fully working Media Center grabbing two HD channels from OTA and playing Divx, Xvid and Dvds right from my computer.