As suggested by the version number, Celestia 1.6.1 is not a major feature release. The main changes are:
- Translation improvements for existing languages, plus six new languages (Chinese traditional, Turkish, Slovak, Norwegian, Galician, and Belarusian)
- Bug fixes
- Data file updates (extrasolar planets, Cassini solstice mission, new moons and solar system locations)
- New HTML help files from Runar and Christian (Guckytos)
The complete list of changes may be found here: http://www.celestiaproject.net/celestia/161changes.txt
Many readers of this forum are probably using the latest SVN trunk version; if that's the case for you, 1.6.1 may not be that interesting to you. But, if you're using 1.6.0, you should definitely get the new version for the bug fixes and updated catalog files.