Anti-halo folk tend to have a PC gaming background, usually hardcore. Debating the value of Halo is akin to arguing about the validity of Wicca to an evangelical Christian. There's just no common frame of reference to have a meaningful discussion.
One thing Halo does better than most PC games is optimize the user experience for the average player: the kind of player that has a limited in-game lifetime (i.e., they die every so often). Hey, that's just like me!
Firstly, the checkpoint system encourages all levels of skill to keep playing. It takes only 4-6 seconds to restore the last checkpoint;.5-1.5 if you invoke the pause screen and restore explicitly. That means you do not have to switch mental modes in order to continue playing after dying; it just happens. Even if you die every 5 seconds, you're still always back in action right away. (Personally, I'd much rather play a game than manage a game; that's just me.)
Secondly, we made sure to optimize the single player experience for a straight playthrough. If you play Halo 2 all the way through, you should never see a long interruptive loading screen. (You will see the Loading... done text, but that's unavoidable for the size and complexity of levels.) Even Halo 1 only had 9 significant loading screens, and those were at appropriate points in the game (i.e., at the end of a level), not in the midst of gameplay. That directly translates into a minimal amount of dead time waiting for the game to start, and a maximal amount of time available to play the game. If you happen to die a lot, who cares? You'll never have to wait for the game to reload your checkpoint; you can get right back into the game.
The immediacy of gameplay is one aspect many just don't understand. Or rather, many that disagree with the success of Halo don't understand. (In my opinion.) My theory is the combination of PC gamer and hardcore gamer results in a type of gamer that doesn't experience what I consider to be the least polished areas of most games: player death. And as such, they don't experience the excruciating experience of restarting gameplay.
Then again, maybe it's all the marketing hype. No, probably not. :)