I recently bought ODST because I am a Halo fan and have played previous iterations.  I am a moderate fan in that I usually finish the single player campaign, play some multiplayer games and then archive the game (or give it to my stepfather J ). 

Two questionable design decisions struck me as strange (perhaps even mean spirited).  I was playing on normal, and expected a decent challenge.  However, I think in ODST the desire for challenging gameplay (perhaps with a bent toward satisfying hardcore Halo players) trumped the fun factor and soured me on the series. 

First, in the campaign you are given a really weak (damage) main weapon - M7S Caseless Submachine Gun.  I found this weapon to be really poor in combat.  Unless you can manage a headshot it seemed like a liability.  Even the headshots only do significant damage on weaker enemies.  The new M6C/SOCOM is cool and perhaps a better overall weapon.  However, onto my second issue, where is my AMMO!

So I am in this hot-zone of Covenant hell, and there is a severe paucity of ammo for my UNSC weapons.  Throughout the campaign I was forced to wield Covenant weapons because my UNSC weapons were always dry.  I felt like a vulture…and a Covenant recruit.

Finally, Firefight stinks when you are alone.   Now I consider myself an above average FPS player, but jeez going solo in Firefight is a masochistic existence.   The lack of UNSC weapons and no ammo is omnipresent, and health is no where near abundant to give you a fighting chance.  

Finally, the fun ends early in that by wave three; Covenant forces are sending Brutes and Hunters with a healthy dose of Wraiths and Choppers to vex you.  UNSC vehicles were in short supply, and at least early on, failed to respawn.  How can a soldier survive and feel badass in these conditions?  I often found myself running around like a scared rabbit.  Even with three pals, Firefight turned into a grind as your collective seven lives were quickly lost. 

So I found myself sort of dreading finishing the game and even shunned invites to play co-operatively because the design restrictions seemed (imo) to suck the fun out of the game in favor of crushing challenge.