I've used Windows 7 Media Centre for the last 3 years for TV recording, and used the Media Browser plugin for movies and TV. However since getting a Freeview HD recorder last year it's taken more of a back seat and no longer used for TV recording.
So I have now been introduced into the world of XBMC and, well............WOW

It's so much more configurable than MCE, much smoother to operate and can be fully controlled via my Android phone
Also, my NAS box which holds all my media also runs a MySQL database to hold all the library information. It also means I can stop a video/movie in one room and resume from that point in another
