Something else we've never done until now is deal with the city's feisty civilians, who aren't at all like the idiot sheep from previous games. The smart ones will bolt at the sound of gunfire or the sight of a gun barrel, but on top of that, they'll behave in eerily realistic ways. If you're blocking traffic, for example, they'll often try to get around you instead of just stopping and honking. If they hit you, they'll get out of their cars to see if you're OK. And if you hit them (or in some cases just bump into them while walking past), well, you might be in for a fight - and depending on how badly other people want to get involved, it could turn into a brawl.
Luckily, you're pretty capable in a fight. GTA IV's "hero," Niko Bellic, is trained in the Israeli martial art of Krav Maga, which is a fancy way of saying he can kick people in the nuts as well as punch them. He can also block and dodge attacks (with the latter usually followed up by a quick sucker-punch flurry), and if his enemies are packing a weapon, he can sometimes disarm them bare-handed.
Aside from being willing to fight back, the civilians also have a strange tendency to occasionally burst into flames when you rear-end them at high speeds. We're not sure why that is, but watching them stumble out of their cars and writhe around makes us feel terrible every time it happens.
Thankfully, the pedestrians are smart enough to stay the hell away when you get into a serious firefight, which eliminates the old problem of accidentally locking onto one of them when you're trying to aim at an armed aggressor. The classic problems with aiming in GTA haven't completely gone away, but gunfights are a hell of a lot better this time around, largely because they've been completely reinvented.
Instead of just plinking away at aggressors while running around in the open, the combat now borrows heavily from games like Gears of War, with a cover system that enables you to flatten yourself against a wall and pull off blind or aimed shots around the corner. This is occasionally a little glitchy - Niko has a bad habit of flattening himself against the wrong side of objects if you're not careful - but overall it works extremely well, and gives the gunfights a methodical, strategic feel that they never had before.
As for the actual aiming - arguably the series' biggest problem since GTA III - it's still a bit finicky when it comes to targeting people who are standing right next to you instead of faraway enemies, but overall it's vastly improved. You can now aim freely with a half-pull of the left trigger, or lock onto individual foes by pulling it in all the way. And once you're locked on, you can move the right stick to target specific body parts (like the face), or just flick it to switch rapidly between targets. Get good at it, and you'll be able to take down mobs of heavily armed goons by just ducking behind cover, carefully lining up a headshot, waiting for an enemy to pop up from cover and then squeezing the trigger once. Beautiful.
If you get capped, though, don't worry - unlike previous GTAs, you won't lose any of the weaponry you've amassed. Better still, if you were in the middle of a mission when you ate it, you'll receive a text message on Niko's phone that'll enable you to instantly restart the mission with no backtracking. This even sets the clock back to the time that you first started the mission, meaning that if your death made you miss an appointment, you'll get a second chance at it. Really, the only drawback is that there are no mid-mission checkpoints, so if you die when you're close to the end of a long and difficult task, be ready to bite the bullet and start over from scratch.
Getting arrested is another matter, though - if the cops take you down, you'll lose all your weapons and a good chunk of your cash. Fortunately, this is really easy to avoid; during the entire game, we were only arrested once, and it was because we wanted to see what would happen. It's simple: when a cop starts to arrest you, just hit X to break away. This will prompt the cop to instantly open fire, but hey, dying's always better than arrest here.
If you can avoid getting shot, however, running from the cops - like so much else - is a lot different from what you're used to. Depending on the severity of your crimes, a big flashing circle - your "wanted radius" - will be plopped onto your map. If you can escape it without any cops seeing you, you'll make a clean getaway. You also have the option of ducking into a Pay 'N Spray for a quick, cop-fooling paint job, although again, this only works if the police don't see you go in. They're not stupid, after all.