I've been using the WD HD Tunner for 4 days now and here are my findings.
After latest firmware upgrade 1.02.07:
To add cover art, take your favorite .jpg of the movie's cover, and drop it inside the folder where the .mvk or whichever file format file is. Name that EXACTLY the same as your video file. Ex, death_race_HD_movie.mvk death_race_HD_movie.jpg. The image must be in .jpg format. The folder in which the video file recides, along with the icon of the video file itself will also display the image file. This only works for thumbnail view.
You can add an image even to other folders by adding your favorite image (in my case I have a Blu-Ray and a DVD folder, I added the blu-ray logo to the blu-ray folder. Just drop inside the folder the .jpg file and name it FOLDER. That simple.
If you rip to .mvk (I use MakeMVK), it will keep all your surround (DB5.1 and DTS) and image quality true to original in one file. So you don't end up with a bunch of little files to sort through. I rip only the main movie, the audio tracks and the subtitles.
ISO's do play, but are buggy specially with Blu-rays. Audio cuts off, audio track defaults to some foreign language and they are huge! None of these problems are present when ripped to .mvk.
I cannot get subtitles to work for some reason.
On the new firmware, you can select different chapters as you play the blu-ray which is very nice.
Hope this helps.