The new features in LyX 2.0 are detailed in
http://wiki.lyx.org/LyX/NewInLyX20
+* Advanced Search Facility
+* Spell-checking on the Fly
+* Compare Documents Feature
+* XHTML Output
+* Multilingual Thesaurus
+* XeTeX Backend
+* Multiple Indices Support
+* Progress View and Debugging Pane
+* Enhanced Instant Preview
+* Forward Search for DVI/PDF Files
+* Enhanced Version Control Features
What's new in version 1.6.7?
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