I understand all that, but there is something to be said for something you dont have to F with through a pc. If I just want to come home and turn the tv on and watch something I recorded the night before I can do so. It even records some stuff that it think I might like based on my previous recordings.
I can watch netflix directly through the main interface also. You can watch amazon on demand or hulu plus through it also.
If I wanted to do a HT pc then Im sure going that route would work fine. Having the scheduler is something I dont think you can get with a tuner card.
For everything I do download though, I stream through my xbox or ps3 with tversity, and through the WD live in the bedroom.
This setup offers the simplicity I like for regular viewing along with being able to do the more complex file types .MKV etc when needed.