I've been using BTV for about six years- I highly recommend it. Currently running on Win7 x32- just as stable as XP was. (You may have problems with x64 versions of Windows though.)
W.A.F. is very high; my wife has no problem recording and playing back her shows. We have several HTPCs and 3 licenses of BTV (really not needed depending on your setup, as BTV can use multiple tuners simultaneously on the same system, but we have several HTPC setups/Sat boxes spread around the house). BTV seamlessly plays back shows from any of the systems in the house over the network, so it doesn't matter in what room a show was recorded.
Com skip: as said, not the most accurate, but I find it invaluable. It produces white-out areas on a recording's timeline that allow you to know pretty accurately where the commercials are, and skip right past them with 2 or 3 taps of the remote.
As for remotes: I highly recommend the Gyration Media Center remote. Yes, it's a little pricey, but it controls everything (PC, TV, receiver, etc.) and in my use has the most logical PC-control as it operates like an air-mouse. It works fine in MC of course, but also, perfectly with BTV as well.
We currently use WMC also to play back our movies and music. It plays perfectly well with BTV so long as you disable the WMC scheduling service and don't try and also use it for TV. BTV can even be made to launch directly from the WMC interface, so it can function as the overall 10ft interface.
BTV records in standard MPEG-2 format, so it's very easy to burn the recorded shows to DVD. There's a built-in 'burn to DVD plug-in' you can buy, or use third-party software. I prefer Roxio My DVD (used to be Sonic) because it doesn't insist on re-encoding the files which are already DVD-ready, so the process only takes a few minutes, rather than hours to needlessly re-encode. [EDIT: actually this is true only for NTSC sources- for ATSC, it's not as these are transport stream files and must be re-encoded for DVD.]
BTV will also automatically re-encode shows to iPhone/iTunes or WMA formats if you want shows that way- very handy for some shows I like to take with me. The options for all these things are the best of any TV software I've used.
Add in Hulu Desktop, Boxee and Netflix online and you'll hardly need anything else to watch.
You should be able to split an antennae signal and run it to multiple sources at the same time. If you split the signal enough to see quality degrade, you can always use a signal-amp.
For HDMI into the TV, keep in mind you don't have to use a video card with an HDMI port- you can buy a
DVI to HDMI cable from somewhere like monoprice, and then use any video card with DVI. Since you'll be running separate optical sound, it's the same video signal anyway.
Make sure the board you choose has optical audio out, or a bracket to add it.
For tuner: if you can use wired ethernet rather than wireless, I highly recommend the Silicon Dust HDHomerun network tuner. I messed with a few PCI ATSC cards before getting our (dual tuner) HDHR and I'd never go back. The HDHR is just set-it-and-forget-it simple, and it pumps out HDTV to any wired computer on the network. (If you're wireless-only, then forget it, it only works wired.)
Also, don't forget a good wireless HTPC keyboard: I can't recommend enough, stick with RF (no line of sight required) not IR. A good built-in trackball, joystick, or gyro function is a must- then you can easily forego a standard remote.
They're expensive, but the
Cideko Air Keyboard looks really good, as it combines all the best elements: RF, small size, PC and Mac compat, keyboard and gyro-air mouse in one device.