Here's details for Grand Theft Auto V that has been found in the 18 page Game Informer article.
- The game will feature three protagonists which you can switch between at any time. Michael, Trevor, and Franklin
- Michael (heard voicing trailer 1) is a retired bank robber living a lavish lifestyle thanks to a deal with the FIB
- Michael has a wife, Amanda, and a teenage daughter, Tracy
- Trevor is a friend of Michael's. He lives in a trailer in a desert region of the map. He is a war veteran and has flight experience.
- Each of the three characters has their own personality, motivations and skillset
- When not in control of a character, they will be going about their daily business - you are free to switch between them at nearly any time you want.
- You can flick off people, with different types of people in different areas reacting differently
- "Within the story, you're going to know information about a character before they know it because you're going to know what the other people know when you play as them"
- No RPG style elements to character customisation, however, you can buy different clothes for each character
- Some familiar faces from GTA IV and EFLC will make a return, though not major ones like Niko.
- Gameplay mechanics have evolved greatly since GTA IV
- Driving is less boat-like as in GTA IV, has more of a racing game feel to it
- More vehicles than any GTA game has ever had before - including BMX bikes, road bikes, dirt bikes, huge variety of cars and trucks, helicopters, planes, ATVs and jet skis
- Shooting and melee combat has evolved, though no specifics are given about this
- Trevor was shown to pick up a can of gasoline and douse vehicles etc. and set fire to it using a lighter
- Rappelling down buildings seems to be possible (at least in one mission shown)
- Los Santos is bigger than Red Dead Redemption, San Andreas and GTA IV combined
- Includes: beachfronts, wine country, large wilderness area, fully explorable Mt. Chiliad, Salton Sea region, military base, sprawling suburban hills, and bustling urban centre.
- The ocean is fully explorable, including being able to dive.
- There are several multi-tiered complex missions like "Three Leaf Clover" in GTA IV
- Missions sometimes feature all three characters, and have a different tone depending on who you are playing as
- Random encounters make a return from GTA IV but appear in a much bigger way
- You will come across dynamic missions in the game. For example you may see a broken down car or a hitchiker. You can choose to stop and interact, or just completely ignore them
- A musical score will increase tension during missions
Source: The GTA Place - Game Informer's World Exclusive GTA V Preview!
- Ammu-Nation makes a return
- Strip clubs, stand up comedy, internet cafes, and television shows all make a return
- Many additional sophisticated minigames will be featured, similar to poker in Red Dead Redemption
- Michael, Trevor and Franklin could have some hobbies only available to them - although most minigames will be available to all three characters.
- Activities include yoga, triathlons, jet skiing, base jumping, tennis and golf.
- Dating will not make a return but you'll have some normal friends to interact with
- Same universe as GTA IV
- There will be "loads of stuff" to spend your money on in the in-game economy, though no property
- The mobile phone concept makes a return, but friends won't annoy you by calling all the time!
Below in the spoiler is the full article. Unfortunately it cuts off a big chunk of it on the site so the source is here: Grand Theft Auto 5 GI Reveal - Imgur. And you can read it in full. I decided to post it anyway as you can see some of the new screenshots