I've always disliked Chris' campaign in RE6 since you're meant to play it more like a cover based shooter. Like the ammo lenience, it conflicts somewhat with the new melee system since it's so easy to be damaged/knocked out of a melee finishing move animation. Also I still hate that you get knocked back when losing a block of health, it's not a big issue in Leon's campaign, but because bullets are flying everywhere it really serves you to not do anything but stay in cover and shoot if possible.
And that first part. I'm playing on Pro difficulty (with skills equipped admittedly), and even during my vanilla runs through Normal and Veteran, that sequence where you have to defend against waves of enemies while waiting for a helicopter to arrive never gets fun. It doesn't help that the game never really gives you a tutorial on advanced maneuvers (dodging, rolling, etc.) and that you don't pick up a single health item until the next area.
And hilariously, when the helicopter did arrive, as soon as the cutscene ended I was melee'd by a Javo and killed near instantly. It was as if he already initiated the attack during before and I had absolutely no time to react.
RE6 is one of those games where you can see how it could be so much better with just some minor tweaks. I know the climbing QTE was hell in the early days of the game, but that inventory... if they ever "remaster" RE6, they need to give you an inventory a la Revelations 2 or even RE5. Just being able to hotkey weapons would improve the fun factor drastically.