Shortly after GTA 5 launched, Rockstar enabled the multiplayer component - Grand Theft Auto Online, which spent has spent nearly the entirety of its existence wracked with connectivity and cloud server issues. Since then, things have settled down considerably, so let's talk about it.
After you create a character, you'll hop off a plane and get picked up by Franklin's friend, Lamar - who serves as your tour guide to Los Santos' multiplayer offerings. Apparently GTAO takes place several weeks before the events of GTA 5, but that's not super important. Once you're introduced to the world, you'll be dropped into a random server of 16 people.
Wandering through the world in GTA Online works much like standard GTA 5, though you'll constantly have to deal with the other players on your server, most of whom are merely content to hunt other players down and grief them. Hitting activity points on a map, or selecting a job via your mobile phone will prompt other players to join your activity, though most will ignore your request and you'll be pulled into a matchmaking lobby to find other players. Most of the time, completing an activity dumps you back out into the open world with another random set of players, though you can choose to stick with your current group if you'd like.
What can you do in GTA Online, you ask? Just about anything that you can in normal GTA 5. Want to play golf or tennis? Go nuts. Want to race cars, motorcycles, or planes? Great. However, we're here to talk about the co-op and it's hit or miss. First, if you came looking for Heists, you're out of luck, as those are going to be patched in at a later date. For now, all you can do are simple jobs, such as retrieving cars, robbing stores, or taking out gang hideouts. If you played Red Dead Redemption, it feels a little similar. There are also wave-based survival and deathmatch modes to participate in, though I'm not an enormous fan of how combat works in the game, so your mileage may vary there.
One nice touch is that whenever you're in a car with another player, you can switch the radio station at-will, which leads to a little back-and-forth if your partner doesn't like what you chose to listen to. It was funny until my teammate decided to open-mic his home stereo. Sadface.
Unless you're big on the anarchy, it's tough for me to recommend GTA Online as it stands. It's stupidly ambitious, but unless you opt out of the open PVP system or set a Crew-only session, you're going to have to deal with a lot of people who are only out to grief you. Standing around looking at your phone? You'll get killed. Are you in a store trying to buy something? Expect other players to stack cars up against the doors so you can't get out. The community surrounding it is (let's be honest- predictably) hostile, and after meeting nothing but rude players, I muted all voice communication.
Ultimately, I can recommend GTA 5 for its single player experience, but GTA Online still feels very much like a beta test. Once Heists get patched in, I'm definitely going to go back for more, but for now it doesn't feel like a place I want to spend a whole lot of time. Perhaps it's just me, but when I play an open world crime simulator, I want to go looking for trouble, but don't want it to come looking for me.
UPDATE: A year later and new versions have changed a lot with GTA. Read on for some updated impressions.