I'd do a couple writeups. The best baselines to start with for the HTPC itself are:
1. Budget DYI AV build with local storage
2. Performance DYI AV/WOW-gaming build with local storage
3. High performance DYI AV/Crysis-gaming build with local storage
From there, everything else is just modifications, like replacing local storage with NAS or a server and passive cooling for silence. Then there are the OEM solutions, which will cost more in $ but give you a simpler setup experience. Those could use some focus in the area of software installs, codec config.
With Vista, making an HTPC remote controlled is a lot easier, but standby modes in the BIOS matter, so explaining to people what to look for and recommending products is a good idea.
Showing people as many cooling options as possible, rather than just suggesting Noctua fans because SilentPCReview loves them, would be good too... *chuckle*
The HTPC case market is expanding. There are so many more options today than years ago. Power supplies are more critical today than a lot of people want to admit. It looks like we're finally getting away from the "More watts is better!" mentality and focusing on their efficiency, amperage output, noise level, and component quality.
Then there's the NMT devices that are getting very popular. I've noticed a lot of sites talk about them or review them, but don't really go into details or have horribly organized information on them. For someone who already has a massive storage array and just wants to stream AV to their TV or receiver, these devices are sometimes a far better solution than an HTPC.
As mentioned earlier, there might be some resistance regarding the ripping of BDs and HD-DVDs. There is commercially available software for the purpose, so we'd be well within our rights to discuss methods of streaming those videos and archiving the discs themselves. Personally, I prefer browsing through my files and picking what I want to use, rather than going to a cabinet, looking for discs, and needing to switch them physically in the player when I want to use something.
Discussing the pros/cons of all these different solutions could shed some light on a segment that's previously been elusive to some people. Plus, there's a section just for interconnects. I don't think a section for Mutimedia Integration would be a bad addition. =)