You might remember that back in December we talked about Windows 95/98 and Windows ME and why their support for the nightlies has been discontinued.
The good news is that the problem has been solved, provided that you download the win9x binary. All users of more recent Windows OS's (2000, XP and Vista) should get win32 to enjoy full UNICODE support.
What is the bad news you say? None :)

On behalf of the OpenTTD team I am proud to present you OpenTTD 0.5.0 (the final version this time). Those who have been us since the release candidates, we thank you for your diligent testing and bugreporting. For the users who are only now venturing to upgrade from 0.4.8, you will see a *LOT* of changes, all for the better. The various RC's have already talked about this, but let me restate the biggest changes since 0.4.8:

We have a new fast, robust and flexible pathfinder, electrified rails support, a brand new terrain generator, full UNICODE support and better multiplayer. NewGRF compatbility (modding) has been greatly enhanced with support for changing stations, adding sounds, more vehicle sets, etc.
The smaller feature- and buglist goes on and on, but we'll let the user explore this. All users of 0.4.8 are encouraged to update to this new release.

Please read the full announcement at the forums as it contains important information for Win9x/WinME and international users.

Instead of the final 0.5.0, we have released yet another Release Candidate, #5 to be precise.

Release highlights of this RC are various fixes for 'cheats' with flooding, Korean, Simplified Chinese and Traditional Chinese translations. For a full list, have a look at the tt-forums post here.

We are getting a lot of questions about bad fonts, only '?' characters for non-latin languages, etc. We would clearly like to state to READ the readme bundled with the game, section '9. Troubleshooting', or online here.

To state this here shortly: you need to specify a font in openttd.cfg in the small_font/medium_font and large_font sections to get proper characters for Japanese, Russian, etc. Some languages have sprite-versions of the fonts available, you can put that in the [newgrf-static] section of the cfg file.

Completely unrelated, but Release Candidate 4 has a bug that it starts up in russian for the first time. The solution is to either try to find your way through all the '?'-s and change the language, delete russian.lng file or set 'language=english.lng' in the config file.

The next Release Candidate (#4 now) is released within two weeks of the previous version. A highly recommended update.

Release highlights of this RC are various desync fixes for a much more stable MP experience, Japanese, Slovenian translations, OS/2 support and the ability to load games without the exactly matching NewGRF files. For a full list, have a look at the tt-forums post here.