The close integration with achievements and game loading is sweet. I am curious how the auto-loading would work with the overarching achievements, like the "Kill X number of enemy Y" type achievements? It would be awesome if the game knew which levels gave you the most opportunities to take out those enemies and let you pick which one you wanted.
I'm still curious how par score and par time are calculated for the different missions. Is it something preset by 343 that everyone can shoot for independently? Or is it calculated dynamically from the scores of the entire community? Depending on how dedicated the community is, the later could be a real bitch.
Regardless, this is going to be a blast!