I’ve looked at the following HTPC software.

MythTV
Free
Linux-based

TVersity
Free

PlayOn
$$
Integrates NetFlix & Hulu accounts

MediaPortal
Free
Works very well NetFlix manager plug-in.
DirecTV DVR cannot see this though.

GeexBox
Free
Linux-based

SimpleCenter

GBPVR
British-based ?

MeediOS
Good but limited development.
Integrates NetFlix account with MeeFlix