3/5 stars. The rules are nicely fluffy. Maybe 3.5 stars on a good day.
The master of the World Eaters is a character that has been systematically used through his life and abused. I have a lot of sympathy for him due to circumstances that he could never control or be in charge of. And for the glimmer of a moment when he was in control and commanded his gladiator's rebellion, he was denied a worthy death by his would be father. Ever resentful and filled with unbroken rage, it is simplicity itself to see why he through in his lot with Horus. Yet he had no particular love of the rest of his brothers who turned traitor either. His is a tragedy that could have been averted many times over. It didn't have to be this way. But by the end of the Heresy, he became a Daemon Primarch and would be forever walking the eight fold crimson path with nothing but his own rage and blood lust for company. We weep for the possibilities lost.
Simply put, Angron is a beat stick (but also comes with army buffing abilities which is nice). By this I mean that his strengths are in close combat (did anyone expect anything less?) and that is where the controlling player needs to get him to with all due celerity.
The Sire of the World Eaters rule gives the army a welcome boon in the form of feel no pain and adamantium will. This will make Thousand Sons players cry. The bonus to movement reactions will also really help to get the army in an optimum position.
The Butcher's Nails grant a bonus cumulative attack increase every game turn, but at the expense of everyone treating Angron at WS=3 for attacks targeting him, much like the Ravening Madmen rule. Meanwhile the Red Sands allow him to enter plentiful challenges and split attacks according to his whim.
His equipment is good with 2+/4++ and a stat line that is reasonable for a Primarch. The weapons are great.
The WS=3 for strikes against him is a weakness. But does Angron care? Nope.
A strong primarch, but not the strongest. Points wise he is about right give or take a few as he has a lot of special rules in addition to an army wide buff. Hence worth taking if the army cost allows.