The carefully-crafted prologue ensures there's a low-level weapon for every weapon skill in the area, and conversational options for all the possible powers of persuasion in the mission to defeat (or, of course, side with) Cobb's gang. It introduces you to the new special abilities unlocked with every melee weapon in the game - a nine-iron golf club comes with a destructive blow called "Fore!" - and New Vegas' biggest new element, a reputation system.
A new entry in the Pip-Boy gives you a perk for a particular location or faction if your reputation with a faction changes. Defeat Cobb and you earn "Accepted" with Good Springs - "folks have come to accept you for your helpful nature". Ultimately, this system plays into the game's principal narrative struggle between the New Californian Republic (NCR) militia, based at McCarran, and a group of slavers called Caesar's legion. If you know Vegas, you can probably guess where you'll find their HQ. Whichever you side with, the other will be your principal enemy in the game.
Other factions like the Brotherhood of Steel and the Super Mutants are around, naturally, and can be played against, for or even toyed with. Avellone shows us an assault on the stronghold of the Super Mutant Tabetha, a mentally unstable, hulking brute in a blonde bob wig and love-heart glasses. It's possible to pave the way to her death by turning two generations of mutants - the tough first generation and the "dum dums" from the military base in Fallout 2 - against each other, exploiting their paranoia in radio transmissions.
This mission is also an opportunity to show off the new interface for companions, which allows you to give them orders via a wheel system without needing to dip into dialogue. We're accompanied by a friendly, funny Latino ghoul named Raoul, who also serves to display the lighter touch of Obsidian's writers. Tabetha's head is blown clean off with his help - and also that of some ridiculous modified weapons, like a grenade machine-gun with an increased rate of fire (weapon mods from the PC modding community have been included in the game).
Our final excursion is to Helios 1, a Poseidon Energy power station occupied by the NCR. Reputation with that bloated, bureaucratic faction grants you access to the station's inner sanctum, where a surfer dude posing as a scientist, calling himself Fantastic, runs the plant at 1 per cent efficiency. Get past the pre-war security system and you could re-route the power anywhere you like: to McCarran to benefit the NCR, to Fremont to help out the local poor, evenly across the whole region... or to the plant's dormant defence system, an insanely powerful orbital laser. You can then command it at will anywhere in the environment: your own, private apocalypse.
Avellone uses it to turn on his NCR allies and decimate their troops. In doing so, he demonstrates Obsidian's gleeful embrace of the player freedom and destructive abandon that were the hallmarks of Bethesda's already legendary revival of Fallout. But there's also a richness, a texture here that really harks back to the original Interplay games - not surprising really, given Obsidian's own Interplay heritage.
That texture is evident, above all, in the warped Americana of the locations: the distant threat, promise and perverted glamour of the Strip; its humble echo in Primm, with its seedy casino entangled in a rollercoaster; a roadside motel community calling itself Novac after a broken No Vanacies sign, with a sniper nest housed in the mouth of a cheesy dinosaur statue; the lonely, bald rocks of Black Mountain surveying it all. New Vegas will give you a chance to unfold your own story somewhere that's at once real and unreal, familiar and utterly fantastical and strange. And that, surely, is what role-playing games are all about.
Fallout: New Vegas will be released for PC, PS3 and Xbox 360 in autumn 2010.