The armour abilities, replacing Halo 3's consumable equipment pick-ups, are permanent abilities on a cooldown than can be equipped one at a time. The jet pack and sprint are joined by a bubble-shield, armour lock (temporary, motionless invulnerability) and holographic decoy. They're pleasingly streamlined and they showcase Bungie's enormous talent for asymmetrical balance, although the inertia-heavy jet pack, with its beautifully tuned controls, grabs all the headlines in the campaign. It's in multiplayer that the armour abilities make a really big splash.
They certainly have a far more drastic effect than the mildly disappointing changes to the weapon designs. Broadly speaking, the human weapons are slightly improved, with punchy back-to-basics interpretations of the classic assault rifle and pistol. But the Covenant armoury has become an unfocused, over-developed mess, ditching Halo 3's wonderful carbine and beam rifle for lesser imitations (the needle rifle and focus rifle respectively) and adding needless trinkets like the plasma repeater and the funny, but useless, knockback effect of the concussion rifle.
Still, you're as likely to have gained a new favourite as lost an old one, balance is undisturbed, and in multiplayer especially the interaction of all these extravagant weapons, vehicles and armour abilities is a wonder to behold. The hologram alone adds a hilarious new dimension to competitive matches.
The armour abilities and excellent new maps alone would be enough to make this the best multiplayer Halo yet. In fact, that's exactly what they do, because although though the deep customisation of Firefight and the well-conceived new twists on traditional modes like Headhunter and Stockpile are all welcome, any multiplayer session inevitably devolves into endless rounds of Team Slayer. You know what they say about oldies and goodies.
It's terrific stuff; multiplayer Halo has its own flavour, its slightly deliberate pace offset by the loopy, free-wheeling chaos encouraged by the weapon, vehicle, ability and map design. With the new loadout system and damage changes, that flavour has only been intensified. But things have moved fast in the world of the online console FPS, and what was once the only game in town is starting to seem like an acquired taste next to the crisp, arcade thrills and Pavlovian reward feedback of Call of Duty. Ranking up and earning currency to spend on cosmetic unlocks for your Spartan seem like mere fan service by comparison with Infinity Ward's ruthlessly addictive structure.
Bungie has other means of fostering community loyalty, however, and Reach is lucky enough to inherit Halo 3's online feature set in all its revolutionary integration and breadth, including the campaign co-op, Theater video editor and the Forge map editor, now expanded into the mind-boggling multi-map Forge World playpen. This is still a textbook example of how online games should be done, and even PC giants like Blizzard have taken notice - just look at the design of the new Battle.net. Bungie will no doubt keep its Halo legacy alive by providing peerless web and community support for Reach years into the future.
Reach captures what you love about Halo, refining it on the multiplayer side and preserving the fluid, dynamic, ever-surprising campaign action that makes most rivals look like clumsy shooting galleries. What it doesn't do is redefine single-player like Halo did, multiplayer like Halo 2 did, or the network game like Halo 3 did. To be fair, it doesn't need to; that work is already done. That it can't stir or excite in the same way as those games, try as it might - and boy, does it try - is a bigger and more perpelxing disappointment, but still small beer next to its accomplishments.
I called it a monument at the start, and that's just it. Reach is an encore, a victory lap, a crowd-pleasing last hurrah for a series that most definitely won't end here, but will just as definitely never be the same again. Halo deserves another game this good, and Reach is a deserving tribute.
9 / 10
Halo: Reach is released exclusively for Xbox 360 on 14th September.