Missed the following post that discussed running Plex under v3.x. But it should be noted that it does require a bit of work to get Plex installed and would probably violate the My Cloud warrantee to do so since your apparently installing a clean OS to the drive rather than using the WD firmware.
http://community.wd.com/t/using-plex-media-server-with-my-cloud/94429/12
Without transcoding one looses a major feature of Plex which is why it may just be easier/less hassle to go with an Android box (like Amazon’s Fire TV or Fire Stick) and load Kodi to it. Then one can use that Android box to stream content from the My Cloud using an TV interface similar to Plex.
Forgot about the ability to potentially instal Plex to v2.x version My Cloud’s that was discussed in the following thread.
http://community.wd.com/t/latest-my-cloud-mirror-firmware-pre-installed-on-brand-new-my-cloud/145284
