To confound those mind-reading reviewers, I'm someone who's never played any Halo game, ever, and yet still enjoyed the amalgamated "feature" cut of this miniseries on its own merits.
It's not perfect, but it's committed and competent. The sets, costumes and props are surprisingly decent for what is effectively a promotional advert, and the actors give it their absolute all. The effects, once they get going, are decent enough and the budget is very well used.
Sure, it's never going to win awards for originality, and the boot camp concept has been done many times before. But it's strongly conceived and written, the young actors are actually age appropriate, and they perform it compellingly.
Once the CGI bugs and that guy from Doom show up, it actually gets weaker for me as a non-player, but it never drops below the level of credible and competent, and that's high praise for one-off limited series.
I got the impression that the cast and crew had a great time making this, and it shows on screen. Not life-changing, but a great lesson in why you shouldn't lower your expectations of what talented creatives are capable of making when given free reign.