Good thing I din't dump my elderly WDTV Live+ , just connected it again to my HT setup. Despite having sluggish UI WDTV plays every possible file format flawlessly including Dolby TruHD and DTS HD Master. And 1080p/24 to top-up already nice set
The Nvidia Shield does indeed serve as a powerful streaming player. It will not only passthrough both DTS-MA and Dolby TrueHD, but it also supports MPEG-2 video, as well as other codecs that are not supported by Roku. But all that does come at a cost. It's almost twice the price of a Roku Ultra, and the Shield Pro is $300. Also, it doesn't have as nice a user interface for playing local media. Kodi (or the Shield specific version called SPMC) provides the best UI, but it's much more complicated than using the Roku Media Player.
Roku is keeping beta testers extremely busy, so I have high hopes the issues are being addressed. Unfortunately, no one can say in this forum exactly what is being worked on.