Good article! Thanks for sharing. I would not have written this, though, because I don't use Media Center. So far, I don't understand the appeal of this application. Maybe if I had a Home Theater PC (HTPC), I would give it a try but when sitting at my PC it's not useful.
I like the bit about codec packs containing bloat that you don't need, but you folks know that I have a far stronger opposition to them. CoreAVC (with Haali Media Splitter) and ffdshow-tryouts are two packages that I use and recommend, so I'm glad to see those getting a recommendation. I'm not familiar with Gabest's Matroska X64 Splitter. I am running Windows 7 x64 but have never run into anything that won't play. Maybe this is because I don't use Media Center.
Stage IV is where I start to depart from the author. First, WMP can play Matroska (.mkv) video immediately after Stage III. There is no need to hack the OS for this! Also, I would say that if you need some dirty hack to make a player work, find another player. I like Media Player Classic Home Cinema (MPC-HC), others like VLC, and there are plenty more. If this Hack7MC utility is needed for Media Center to play .mkv video, then that is another strike against it.
Stage V, I don't understand the need to make ffdshow-tryouts the preferred DVD decoder over the built-in Windows decoder. I have never seen the "choppy video playback thanks to the (poor) Microsoft DTV-DVD decoder", but that would certainly be a reason to switch for anyone who does. I do like the utility that allows you to change the preference of DirectShow filters -- that's new to me, so I will have to look it over.
Stage VI: ogg and flac media is so rare that I have only toyed with them. It's nice to hear a recommendation for filters in case these formats ever become prevalent.