That's one; I've used that several others over the years, including gb4e and Covington packages. But yes, expex is probably the best now.
Not quite relevant, but we actually composed our grammars in a variant of DocBook XML, then converted them automagically to XeLaTeX for typesetting. Andy Black has a similar toolset that starts with his own document-oriented XML and converts this to XeLaTeX. I stole (with his permission) the code to convert XML interlinear into a LaTeX interlinear format.
Not quite relevant, but we actually composed our grammars in a variant of DocBook XML, then converted them automagically to XeLaTeX for typesetting. Andy Black has a similar toolset that starts with his own document-oriented XML and converts this to XeLaTeX. I stole (with his permission) the code to convert XML interlinear into a LaTeX interlinear format.