WD TV Live (2011)

Pros: - Best value product in it's category "Media Player"
- Works with USB keyboards.
- Wireless AND Gigabit port.
- Multiformat player (much better than Roku)
- More Service Providers than in Blu-ray players.
- Easily sees and connects to other network device

Cons: - GUI is hard for novices (Roku easier)
- Firmware updates from WD can be problematic.
- DLNA functionality could be better.
- Many less Service Providers than Roku offers.
- Occasional lock-ups requiring reboot.

Summary: NOTE: I own the previous WD TV Live PLUS, and previous model Roku without wireless capability. I do not own the most recent models of these two products.

My spouse likes the Roku because of the friendly GUI. But i prefer the WD because it can do so much more than the Roku.
The WD unit was originally developed for streaming from your local network; Netflix capability came later. Roku was originally made for Netflix, but has been expanded with 200+ apps and Service Providers. They have both followed their origins. Roku has never offered their own application to do local network streaming, although they keep hinting.

There have been several Roku-based LAN streaming apps offered by third party developers (hobbists). I tried one which was very complicated to set up, it did not work. Another app was easy to set up but was way too slow to use, and had limited codecs. A third app was so complicated and invasive I didn't try it.

Best Summary:
Buy Roku if you are mostly interested in Netflix and other internet sourced media.
By WD if you want to easily connect to other LAN devices to listen and watch your own media. If you are tech-savy, this is a very fun unit.
Those of you that fall somewhere in between will have to study the two choices carefully, or buy BOTH!