ASUS O!Play can transfer 30-40 Mbps over LAN, this is not enough to play Blu-Ray remuxes over LAN. Not sure that WD TV Live is any better in this sense. You can still use a US hard drive to play such videos.

The biggest disappointment about both WD TV Live and ASUS O!Play is that they don't support Hulu. HTPC with XBMC is a more flexible solution, although the one supporting 1080p MPEG-4 AVC videos will cost much more than network media players mentioned above.

Also I would like to mention that some newer TVs are DLNA certified, so that can play content from your network. This requires you to have a DLNA server software on your computer, but there are several free options available for Linux, Mac OS and Windows.

Although WD TV Live is not ideal, I prefer it to Asus O!Play.

What network media player do you prefer and why?