For anyone actually looking for the ultimate HTPC, I've tried pretty much everything and the absolute best I've found is a combo of an Apple TV with Beamer.app [0] to play just about anything and everything with a great UI, awesome Netflix support, iTunes renting/buying, etc. etc. etc.
0: http://beamer-app.com/ (I'm not affiliated in any way, other than being a very satisfied customer that has had several feature requests fulfilled by the author)
Barebones box with intel atom, a bit of ram, and a small HDD is cheaper and does all that, and you don't have to deal with sidestepping Apple's odd file format restrictions. Throw XBMC on there and you're done, for about $150.
Never heard of Beamer, but I rarely stream/control video directly from the laptop. I've been using Air Video with both the iPad/iPhone (http://www.inmethod.com/air-video) + Drobo for media storage and it works like clockwork. I will still take a look at Beamer.
I bought this app 2 days ago. I have a video that plays perfectly fine on my laptop but on the Apple TV the video goes blank after 15 minutes. It was a choice between them and AirParrot. Although it was cheaper I didn't need the mirroring AirParrot provides.
No. It requires your files to be a format iTunes understands (which mostly limits it to stuff bought in the i-store) and in a iTunes media-library on a PC running on your network. Which for most non-Appleheads is pretty bad and for some (like me) even a no-go.
It could be worse though. In the olden days you had to synch the media to your Apple TV before being able to play it.
0: http://beamer-app.com/ (I'm not affiliated in any way, other than being a very satisfied customer that has had several feature requests fulfilled by the author)