Background, assets and music is a big
Mission outline and storywise developments ok on both missions, they seemed relevant and not just a "filler mission", kudos for that cause it's really hard to achieve.
Checkpoint system: win. THANK YOU!
I found the missions quite a bit fast-paced.
The dialogue (along with the mission progress) was just way fast for me to keep on it, half of the time I didn't know what to do!, IMO only a handfull of missions in a campaign should be as fast as these two were.
The directives list was not helping, press f6? for what??, press f7?? for what?, It diverted my attention from the battlefield, I pressed those in the hopes it would help me do something only to realize they were there to help me target the objectives
Note that this is not a bad idea, actually I use the same system but I found it better to just put a line saying: "destroy x wing (F6)", that way the player knows he's got to destroy wing x and to target he must use that key.
For the sake of keeping the player sane, and yourself while fredding and testing, try to keep your missions under the 10 minutes mark, if it goes up you can either go for the checkpoint system, maybe even consider splitting the mission in two or removing something from the mission objectives as well.
Of course these are all things I think are important, I hope you don't mind me pointing them up.
Anyways, nice job so far... that last mission got me really into the story so I'd say the demo fullfilled it's purpose.