UPDATE – This has now been released as the official firmware(known as 1.03). There are no differences between 1.03.01 and 1.03.
What’s New?
Prerelease 1.03.01 (includes all previously released updates)
Resolved Issues:
* Resolved the language displayed as OFF when English was selected
* Resolved the “Contains” button displayed as “ContainsWWW” in the search function
* Resolved MKV audio which [...]

After months of inactivity a new release is finally out!  Remember, this is still a beta release.  Here’s whats new:
Resolved Issues:

Resolved issue where UI Language displayed as OFF when English is selected.
Resolved UI issue where “ContainsWWW” shows up in the search menu instead of “Contains”.
Resolved MKV audio/video sync issues.
Resolved issue where songs were displayed in [...]

Sorry, we’re a little late on this post.  WD has released 1.02.10 Beta to the public with a few bug fixes.  Here is a quick rundown:
“What’s New?
Prerelease 1.02.10 (includes all previously released updates)
* Greek subtitles render slowly in Greek character encoding mode; subs render properly now * Korean subtitles disappear during the video [...]

After about a month off, WD has finally released a new beta firmware today.  It hasn’t been officially added to their prerelease site(as of the time of typing this) but it is available on their server.  From the readme:
Bugs fixed in 1.02.08:
-Some characters still missing from Greek font
-VC-1 MKVs playback poorly
-Audio out of sync during [...]

Western Digital’s latest beta has arrived, only a few days after the last beta, with a few minor fixes.  Fixed items and additions:

Added option to toggle subtitle default to ‘On’ or ‘Off’
Added subtitle outline thickness selection
Added hard drive spindown on WDTV power off

Download here
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This is a prerelease version of the [...]

Western Digital has released a new pre-release beta firmware version. No official release notes to be found yet but these are some quick notes:

Windows-1250 Central European encoding added
Subtitle rendering quality improved
AVI loading time improved
Fixed an issue where thumbnails weren’t loading sometimes
Thumbnail loading times improved

Download here

This is a prerelease version of the firmware. Feel free [...]