I gave up on WD TV’s streaming function quite a while ago but have hung onto my unit for a while and used it exclusively for file playback. As we all know, the Amazon Fire HD and the Apple TV units have never had USB drives. In fact, that’s why I bought the WD in the first place - it would play some files the Roku 2 would not. That became even more valuable a trait when Roku removed the USB drive from the Roku 3.
All that has changed with the introduction of the Roku 4. Lost in all the fuss over 4K and whether it is better than the new Apple TV, the Roku 4 has a USB drive and it plays back files that the Roku 2 would not: Roku 4 only: H.265/HEVC (.MKV, .MP4, .MOV); VP9 (.MKV)
No, it won’t play back .avi files but I don’t see many of those any more and I can convert them with Handbrake.
I’ll keep my WD TV but my guess is that it won’t get much use from here on out.