In our living (movie) room I have an XBox 360 acting as an extender, as well as an ATV3 and Blu-ray player. It also has an Acer Revo 1600 nettop PC (ATOM/ION CPU/GPU) running the Plex client so that we can play my HD movies (no transoding required). These devices are connected via ethernet (gigabit, in the case of the Revo).
My daughter's room has an XBox 360, an ATV2, and an older Blu-ray player. There's no clean way to run ethernet cable to her room so when she fires up the XBox 360 to watch TV she consumes a lot of our intranet bandwidth.
The Plex server app is great for gathering all of the metadata and storing it in one central location. The iPhones and iPads can then pull up all of my movies and TV shows, complete with coverart, show descriptions, etc., and the Plex server app (combined with the power of my server's i7 CPU), will transcode my Blu-ray .mkv rips and WMC .wtv shows on-the-fly and maintain great PQ. I can even then use AirPlay to push the content from the iPhone/iPad to an ATV. Downsides are that the Plex software does not (currently) support 5.1 audio or Blu-ray subtitles. Another issue is that the Plex server app isn't smart enough (yet, I hope) to grab the .wtv shows as-is and needs help from that script I mentioned previously (WTV-MetaRenamer). Unfortunately, that script gets its metadata from TVDB (if memory serves) and comes up short, not finding the proper info for a good number of my .wtv TV shows.
For live TV, I can use InstaTV Pro on the iOS devices to tune in any channel. The app interacts directly with the HDHomeRun Prime tuner, so there's no transcoding going on. Remarkably, my iPhones and iPads seem to be capable of playing the native MPEG-2 HD content. The app is buggy/glitchy, though, so I'm not sure if some of the issue could be due to the high nitrate of the source material. Still, it's pretty impressive.
In an ideal world, the WMC server would transcode on-the-fly all of the incoming TV shows and store them as MP4 files, allowing my client devices to play them back without needing the server to do on-the-fly transcoding at that time. That could theoretically also open up the possibility of the client devices playing back live TV and even having pause/rewind functionality (where it would be relying on WMC to do that work for them), but alas that is not the case and I guess will never be, since Microsoft doesn't seem to be interested in continuing work on Media Center and no other software company has done the work of trying to get CableLabs certified. If you can live without cablecard-dependent channels (i.e., OTA or ClearQAM), then there are some options that seem to come close to offering that, but I'm not sure if even those do what I'd like. For instance, there is the Elgato software for the Mac that will do MP4 conversion, but I don't think it does on-the-fly conversion, so I don't know/think that you could, for example, watch a live TV show on your iPad and pause it.
I suppose eventually we'll see more options come out, perhaps by the cable/satellite companies, or maybe TiVo building its transcoding hardware into a new all-in-one multi-tuner box. SiliconDust showed off some sort of new version of their HDHomeRun Prime which looks to have on-the-fly MP4 conversion built-in, but I'm not sure how that will all work. They still need some sort of "server" somewhere to schedule/record the shows, since I won't be recording them directly onto my iPad/iPhone's limited storage space, and a live TV-only (no pause/rewind/DVR) app is of limited interest to me. But hopefully they've got some exciting things planned.
I've also thought that MS seems to be acting really stupidly by not leveraging their Media Center server expertise and adding on-the-fly MP4 recording to be used in conjunction with their own Windows Phones that they seem to want to sell to people. If they made something proprietary that only worked on these phones, that could potentially be a killer app that could sell more of their phones. Instead, they seem to be deprecating Media Center altogether, and instead are interested in having the XBox 360 be the main hub where you'll get internet-sourced media, including purchasing TV shows and movie rentals a la carte, similar to Apple's iTunes store.
Anyways, I thought I'd start this topic up here in case there were others doing similar things in an iOS-centric home. Post here so that we can exchange ideas.