As a Squeezebox owner, I already have a media server setup for distributing audio around the house. I've been considering one of these "Media Tank" devices, including the Popcorn Hour and a few others.
Colleagues of mine own the WDTV (original), WDTV-live and the Patriot. The consensus of online reviews is that the ASUS O!Play does not provide as clear a picture as the others.
Feedback from a colleague on the WDTV was positive, except for the fact that running native FW, it wasn't networked. Other colleagues jumped on the WDTV-live when it first came out and raved about the improved performance over the original box. One guy complained of stuttering on 1080p playback over the network, but said this is now fixed and rock-solid with the latest FW upgrade.
I spoke with the first guy that owned the WDTV in my office today and he excitedly ran out last week to buy a Patriot, mainly for the portability aspect; take the unit to the cottage w/ content on the internal HDD.
Today he was complaining that while the Patriot was fine accessing content from the internal drive and an external USB drive, he was not able to get it to see network-shared drives.
Based on the experiences of my office colleagues, if I were to purchase a unit today, I'd probably opt for the WDTV-live.
When the unit first came out, it was selling for $129 at CanadaComputers and $169 at BestBuy. Some of the guys I know were able to get BB to price-match on CC when they had stock. Also note that in the US, BestBuy is selling the WDTV-live for us$119. I'm heading to the US for Thanksgiving and my pick one up, especially since I notice that CC, NCIX and others have now jacked their price to $139