I have prepared my wallet and my anus, take it all Valve, take it now!
That said, thus one is like a damn supercompendium. For 10 dollars you get all the cool shit from the Winter Battle Pass (quests, betting, wheel of fortune) plus the compendium stuff like stretch goals, prize pool contribution, predictions, team and player pages, arcana vote, MVP match vote etc. I couldn't give a shit about the mmr reset as I don't play ranked (I calibrated for party and solo just under 4k) and pretty much just go all picking all the live long day.
But the hats...Jesus the hats. Immortals, terrain, taunts, courier, spell effects, that nonsense with the river. Dear god I want it all, starting with the omni hammer, enchantress rainbows are pretty sweet too.