I haven't yet made my probably-uber-long post summing up my feelings about the campaign, but this seemed like a relatively-short way to toss out a few points, so here goes:
I identify with the FederationAfter what we saw during that campaign, I can't see how any rational human can have more than a shred of empathy for the Alliance. The GTVA are a bunch of invading, lying, manipulative, murderous war criminals, betraying everything that they purported to stand for. It's my sincere wish that they receive their comeuppance in one form or another.
I used a checkpoint at least once in the campaignYeah...a bit more than once. Some of those showpiece missions were brutal.
I threatened the hostage in M05I felt like calling the bluff would swiftly end in everyone getting blowed up, so I decided to put a little pressure on that poor little spacesuit inhabitant. I didn't even intentionally up the ante by flying next to her...I was already sitting there when the directive cleared, so I sort of fell into it by accident. The choice seemed in-character for Noemi at that point, and it felt like the best way to buy the most time. I did try replaying the mission in the Tech Room and calling the bluff, but I wound up getting myself killed by accident, and I haven't tried it again since.
I thought Darkest Hour was just rightThe first half of my playthrough is a bit of a blur in my memory, so I don't remember any specifically awful difficulty about this mission. I probably died once or twice, but it wasn't a huge deal. I wasn't making any sustained attempt to keep the rookies alive, though...I have enough trouble watching out for my own skin.
I killed Xinny and ZeroSee below.
I let Xinny and Zero shoot me downThere was no "letting" here...I got my ass royally handed to me the first time through, and I didn't stand a chance against them.

After seeing the recommendation text, I decided to give it another shot, and I managed to take them all out. As the dialogue unfolded, though, I felt like I had been kicked in the gut, and I sort of wish I had stuck with the first outcome.
I found the Simms conversation easyI decided to go with the direct approach, based on the briefing hints and what I knew of Noemi's personality, and I worked my way through it without a hitch. I am curious as to how the other paths would have turned out, though.
I found the Nyx dogfight too hardI didn't so much kill them as fly around afterburning like crazy hoping that someone else would.

I did manage to make it through, though.
I understood the pointbuy system in AristeiaI didn't exactly get what each option entailed when I made the first choice, but I got the gist of it after that. I had to replay the mission once or twice, so that helped too. Really cool mechanic.
I thought the Vasudan logistics incident was a terrible accidentMy heart fell into my stomach at the way that one turned out. That situation held such promise, and then that other asshole frigate had to jump in guns a-blazing and destroy it.
I felt good in One Perfect MomentBeautiful atmosphere, beautiful music, beautiful character development, pretty much beautiful everything.
I was shocked and appalled by the assassinationHow low can the GTVA sink? That low. Cowardly swine.
I really loved the soundtrack at the end of PawnsI can't even for the life of me remember what the hell it was, but I know I thought it was awesome.
I thought Delenda Est was too hardThe first minute or two of this mission kicked my ass every single time, even when I finally managed to beat it. Those first incoming bomber waves were
brutal, and the Indus was usually at 50% integrity or lower by the time they were finished. It didn't help that I really didn't understand how to use Slammers. If there was some way to tone that attack down a bit, even just a hair, I think it'd help.
I want to kill Admiral SteeleSee first answer.

I'd have no qualms at all about introducing him to the business end of an Archer.