I mean, to me the value of an HTPC is music and DVR. It does both ridiculously well at a very inexpensive price. Different specs I've put together have gotten me under $900 for a very capable, really good looking piece of equipment that will look nice with the rest of my stuff. But once you add in blu-ray, things change. Suddenly you need faster processors, better cooling, add-in programs, hot running video cards, more memory, better/bigger cases... all to really struggle to get bd that will likely not be of the same quality from a standalone player.
Until, I can just install Vista, a decent HDMI video card bitstreaming lossless audio, and just turn it on and go... I think I'll pass. i'm all for tweaking and fiddling, but who wants to have to load multiple programs just to run a disc?