If you've been in the hobby a long while, you'll be aware of the unspoken creed that primarch's will never get statistics in any rulebook. That was broken in Apocalypse when Angron (as a deamon primarch) acquired some statistics.
Now, Forge World are poised to not only release game play stats for all the primarchs, but also do the miniature range. I'm not sure I can resist collecting the entire set of 18 (maybe 19?) primarchs! But seriously: have a read of the leaked rules if you haven't already done so. Angron is a sheer beast. He hates everything. EVERYTHING! He is able to divide his attacks between multiple challenges and thanks to his "Butcher's Nails", he gains extra attacks as the game goes on for kills he makes. Weighing in at 400points, he can take on anything in the game and do well against it toe-to-toe.
Horus is also leaked, costing 500 points with different rules that reflect his tactical genius and decapitating strike approach to close combat. I'm looking forward to seeing what they do with the perfection approach of Fulgrim, and the sheer "he won't die" quality of Mortarion.
Heck, I'm completely intrigued about what Alpharius (Omegon?)'s special abilities are going to be. Something infiltrat-y and sneaky, I bet. And, I hope, these primarchs will evolve over the course of the Horus Heresy books that Forge World will be releasing. Tis a good time to be a chaos player once more!