Keeping in mind that my brother was new to the game: my brother was equipped with the default handgun. I was rocking a submachine gun, mostly for the purpose of shooting while driving. The other team was making a long trip around, so we cut through a couple of alleys (at the cost of both headlights) and swerved out onto the street just ahead of our foes in their shiny new SUV. Suddenly, the enemy passenger bailed out and crossed the concrete barrier in the median of the four-lane road - I think he was headed for the beach. I saw an opportunity to run him over, since my horrid driving-slash-shooting was rendering my aim useless.
Mexican standoff, GTA-style
Without painting too convoluted a picture, the circumstances ended up that the runner became pinned between the two vehicles in a head-on collision that should have killed him. My brother pulled the trigger and as luck would have it gained two headshots - one for the pinned player, and one through the windshield of the SUV. What teamwork, eh? Of course, I took as much credit for it as a wheelman can take...
Since then, I've ventured online only a handful of times. To be honest I can't compete very well with the stellar players that play regularly. But I have found myself in some really interesting situations, usually only survivable with good teamwork. Many other team-based games can claim the same...but how many put you smack in the middle of a city and expect you to maintain proximity to and communication with your teammates? Not many. This generation of co-op seems to impose boundaries on you and your partner - like tethering - either for tech limitations or in order to "optimize" your experience.
Do I really even need to comment?
Personally, I like the freedom that GTA IV provides to online players. I'll admit that things get boring if you don't have some kind of objective, but if you have a cunning and communicative team, your objective can be met amidst possibly the most sprawling, chaotic, and extremely fun battlefields in video games.