There aren’t many new features since 8.3.0 (better JSON language support, better offline eval, sparse parameter support), so this version simply addresses a number of issues that have shown up over time
8.2.0
Many things added including more sophisticated contextual bandits, the recall tree, and OjaNewton.
7.10
No significant changes from 7.9---primarily bugfixes.
7.9
Primarily updates to learning reductions modularity.
7.8
<a href="http://hunch.net/?p=222592">A post</a> with some notes