In addition to everything stated by others, Plats also get the "Unlimited TV & More" IFE pack for free on domestic A330 flights (regularly $7).

But if it's free upgrades you're after, you'll be sorely disappointed since HA is very stingy on free mainland upgrades (2/yr per elite) compared to their peers...and they pride themselves on that too.

HA isn't UA in that they give away 2/3's of their F seats to elites for free; the majority of HA flyers in F on mainland flights have paid for those seats be it in $$$ (F fare or upgrade at T-24) or miles.