From the review:
"The AI is terrible though, it often attacks the wrong enemies, even if you told it not to (with the Q key), it also takes forever to resurrect you in case you go down. In other games this hasn't been a big deal—just let the stupid AI die and fight it out on your own. In Youngblood however, a timer starts as soon as one player is down, and if that player doesn't get resurrected in time, one of your three shared lives is gone. This means that when the AI fails yet again, you have to stop shooting, run to your downed sister and resurrect her. The shared life concept would have been tolerable, were it not for the game's save system, which is non-existent. There is no checkpoints and once you've used up all your three lives, you're right at the start of the level, with all enemies respawned and objectives undone. This is extremely annoying during boss fights, particularly at higher difficulties, because it'll take you almost an hour to reach the boss, a route which you have to repeat in case you die. It also makes short gaming sessions impossible, because quitting the game puts you right back at level start."
That's the part that puts me off on this game. I don't really care for escort missions in general and it sounds like this entire game is one long escort mission. They aren't too bad when the AI is good but when it it's not it is just frustrating at times.
No checkpoints is bad also.