And this is very much about tweaking in the inventory. Borderlands drops loot like a brain-damaged burglar. The entire world is heaving with money, weapons, health vials, shields, grenade mods and class modules - all of which you have to slot into limited inventory space. You're constantly examining stuff - via handy pop-up dialogues - to see how it compares to this sniper rifle or that sub-machinegun.
You develop favourites as you play, and start to actively seek out particular mixtures. Weapons have a number of variables, including rate of fire, accuracy, reload rate, damage, and various other modifiers, such as whether they deal extra "elemental" damage. That means setting things on fire, corroding stuff, and so on. This loot-gathering becomes compulsive, especially since the possibilities for drops are so vast. You just have to keep searching for that perfect rifle, that suitable shield that happens to heal as you play. (Pro-tip: get that kind of shield.)
The other reason the game picks up after some time investment is that it expands slowly. The starting area is surprisingly large, but you run out of novel things to do rather rapidly. As the game moves into its core hub, the town of Newhaven, you begin to see the true scope of it, and to genuinely need the fast-travel system you've unlocked, and the weaponised buggies that can be procured at outposts across the landscape. Borderlands is a towering slice of gameworld, larger than half a dozen straightforward shooters put together.
The Borderlands world, as you've no doubt already seen, is a kind of science-fiction post-apocalypse. It's an alien world covered with the trash of war and messy colonisation. While the tech level is high, thanks to shadowy space corporations who once exploited the world, the state of things is backward and mangled. It's a world of robots and computers filled with shotgun-toting rednecks and cannibal mutants baying for blood. Gearbox has realised it beautifully, and it's a fantastic place to go adventuring.
By this stage in the review the shooter fans are probably screaming to know what Borderlands is actually like as a shooter. Well, it's a better gun-game than Fallout 3, and that's because it is in many respects an fairly traditional FPS. It's got a Halo-style shield recharge, and whether you hit someone largely depends on your personal skill, although there is some spread and wobble in the different guns, which I presume is defined by the accuracy stat. Headshots do more damage, although it's a "critical" in this case, and that may or may not be a kill depending the other factor the game introduces: level difference.
It's not the case that the game simply levels up with you, although it does to some small degree. Enemies will be higher or lower level than you depending on the area you're in and the mission you are doing. Fighting enemies at a similar or lower level than yourself makes the experience rather like a typical FPS, with enemies taking just a couple of hits to go down. Higher-level or "named" enemies, however, will need to be pumped full of damage to be defeated. It's not realistic, but it is highly entertaining. Weapons feel right: the effects are beautifully moderated so that when you get something more powerful, with a higher rate of fire, you really know about it. Fast-firing bazookas are a near-comedy mode of killing things.
The enemies are generally rather entertaining too, but they do run out of interesting tricks long before the game is finished. The non-human creatures are often boringly straightforward - they have one area you need to aim for to take them down with criticals, and they'll generally just charge at you. Humanoid enemies are rather more challenging, as they will retreat, use cover, and fire at where they last saw you.
There is a modicum of intelligence to them, but it regularly fails, with enemies freezing or failing to use cover in a useful way. They are entertaining to fight, however, especially when you're up against a selection of bandits. These come in a pleasant range of mutated varieties: slow-moving bruisers with heavy machineguns, flaming hatchet-chucking psychos, and nippy little midgets with shotguns that blast them onto their arses.