I use two methods in my house currently
HomeTheater - WDTV Live Plus. Love it, plays everything I throw at it. Access its content through simple network shares currently. I'd use a NAS, however....
Bedroom - TiVo Series 2. For streaming, kind of a pain in the ass. Mostly because it doesn't support anything natively, which mean all content has to be transcoded for it. Requiring me to run a pyTivo server just for it.
Hence I'm currently not using a NAS