Seriously I've had countless amounts of occasions in Halo were it became impossible to play. Something like ODST, the checkpoints in that game were perfect. Wether it was after I killed a group of covenant or when I just found a supply cache the checkpoints couldn't have been better.
Edit: For checkpoint problems they should make some sort of system that if you die over 7 or some random number amount of times immediately after a checkpoint, it asks you if you want to restart to the previous checkpoint.
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Even if they don't add more checkpoints, they should at least troubleshoot them more than they did in Halo Reach. Those we're usually fine, but at one point in Long Night Of Solace, it gave me a checkpoint just as my ship blew up, causing me to die again and again every time it reloaded the checkpoint. As long as they can avoid glitches like that, I'm good as far as checkpoints are concerned.