So, rather than posting scans (which I'm pretty sure is against forum rules), I'm going to just post some info from the Game Informer reveal article.
I'll be actively updating this and cleaning it up a bit as I go through the article with a fine tooth comb, so stay tuned.
If you really want to get everything, I encourage you to pick up a copy of the magazine, digitally or when it hits news stands. Support magazines, a dying form of media.
EDIT: As a mod has informed me, apparently links to scans are ok. So here they are (until Game Informer issues a cease and desist to whoever posted them): http://imgur.com/a/GsODP
Retired and in this early 40s. Former bank robber in witness protection. Lives a luxurious life style, but money is running out and he needs to get back in the game. Doesn't get along with his gold digging wife and has trouble understanding his two teenage daughters. Also has a son, Jimmy, that is a lazy twenty-something pot-smoker.
Career criminal in his early 40s. Drug user, loose cannon, former military pilot that worked with Michael on a few jobs back in the day. Has a neck tattoo that says "Cut Here" with a dotted line around his neck. "Completely revels in chaos".
Mid 20s native of Los Santos. Currently a repo man working for an upscale car dealership. Fit and fashion conscious. He's looking to hustle and make his way up the ladder and hooks up with Michael to do that. The young and capable one of the bunch. Tired of being held back by some of his idiotic and dangerous friends.
- You'll be playing as all three main characters and be able to swap between them at almost any time.
- When swapping between them outside of a mission, you'll get a Google Earth style zoom out and zoom in.
- Characters will continue on with their lives when you're not controlling them, so they could be in any number of situations when you jump into them.
- You'll also be swapping between characters while in a mission (through a radial menu). The transition is smooth, quick, and doesn't slow down the action. An example given is a mission where you jump between Michael who is rappelling down an office building (Rainbow Six style), Franklin who is covering him with a sniper rifle, and Trevor who is in a chopper over head. It sounds like you might be restricted a little as far as when you can change, but it all sounds like it's intended to keep you in the action at all times.
- When you include interior and exterior environments, GTA V's Los Santos is bigger than RDR, GTA:SA, and GTA IV combined.
- Focus of missions is having multiple complex multi-tiered heists like "Three Leaf Clover" from GTA IV and the casino job in GTA:SA.
- The characters will primarily reside in different regions while not controlled, so you can quickly jump around the area by jumping between characters. Michael will primarily be in the upper class Rockford Hills, Trevor will reside in a trailer in the middle of the rural/desert area of Blaine County, and Fraklin will be mainly in South Los Santos.
- Transportation includes the return of bicycles and planes, along with dirt bikes, motorcycles, jet skis, helicopters and many types of cars and trucks. Vehicles are more detailed, more numerous, and more varied than any previous GTA.
- There seems to be the implication that each character has unique capabilities. No indication of what that actually means though. Speculating here, but it might be things like only Trevor is able to fly jets or possibly differences in running speed.
- None of the GTA:SA stat building nonsense.
- Driving physics model has been tweaked from GTA IV. Whereas cars were "big and boatlike", they'll now "hold to the ground a bit better". Dan Houser says that it will scratch the itch of "high level racing games".
- Shooting and melee have also been improved. Houser says that shooting is still the focus though, so don't expect anything too great from the melee.
- There's some sort of gesture system that includes giving the finger.
- A single city stretching from beach fronts to a fully explorable Mt. Chiliad. Miltary base among other features. There's also a fully modeled and detailed sea floor that can be explored while scuba diving.
- A lot of side activities, some of which are unique to a particular character and only make sense for someone with their background. Includes things like base jumping, yoga, triathalons, full-fledged golf game.
- No romance stuff, but each character will have their own set of friends. Cell phone stuff has been streamlined to prevent interruptions. A lot of things you used to make calls to do are now just icons on the map.
- GTA IV style casual encounters with people on the street and RDR style random occurrences and dynamic missions (examples include picking up a hitchhiker, finding some wrecked cars in the desert surrounded by dead bodies, and chasing down a purse snatcher).
- A "vibrant and fun" economy. Apparently you won't be building up your empire through property purchases, but "there will be loads of other stuff".
- Not talking multiplayer at this time. They do mention briefly though that the Max Payne 3 "Crew" system will carry over.