A major annoyance with all the Halo games since Halo 2 (I forget how the original Halo was, so I can’t condemn it) is the stupid save system. You reach checkpoints as you play the game, and generally the checkpoints aren’t too far apart, but they usually aren’t as frequent as those in the Gears of War games. The problem is that the Halo games don’t actually save your progress at the checkpoints -they just mark a restart spot if you die. If you really want to save your progress, you have to choose the “Save and Exit” (or similar) in the menu, which actually saves your progress to disk so you can resume later. I learned this the hard way in Halo 2 and haven’t messed up since.
On the other hand, Halo Reach did manage to mess up my save of last night and instead restored me to a much earlier position, thus wasting more than an hour of my time. It put me back before the fighting in space (which I was okay with repeating, because it’s the best part so far). I am certain I properly saved before shutting down for the night last night, but when I started it up today, it put me at the wrong spot. Now I don’t trust it at all and am saving every half hour or so, in case it decides to forget where I am again. Bloody annoying.