PSA: Using Lyx With Native OS X Spellchecker

Lyx 2.0 and onwards on OS X will use spellchecker provided by the OS X. Note however that the language it will use for spellchecking is determined by the document's language setting, not your system language setting.

Furthermore, in version 2.0.3, if you change your document's language setting, you have to close and re-open the document before it takes effect.