I just finished Pillar of Autumn for the campaign Challenge. I decided to try and flawless cowboy it on Heroic with Thunderstorm on. So I really, really took my time, meticulous as hell, systematically dismantling encounters. Took a full hour, but I got through to the big mass driver sequence.
Where I died because I mis-remembered the warped priories I'm supposed to memorize. Don't shoot the two Phantoms hovering in front of my face but not shooting, aim for the Banshees I can barely see in the distance but need to be killed right away or they'll kill me. I feel cheated, and I hate that feeling.
A memorization based sluggish mini-game to end Reach is about the wost way it could have been concluded. I'd sort of forgotten about it, and but it's one of the reasons I don't play PoA to begin with. It, like the rail rides on the Falcons, are the kinds of things the designers of previous Halo titles knew better than to include. I wish it wasn't in Reach.