Version 4 is out now. If you noticed in the comments, the changelog had already been posted. Since then, there have been further improvements, such as the addition of an FOV Slider and Mouse Smoothing checkbox to the options menu while changes have been made.
- Introducing, Extra Missions! These are a second, Irrational-quality campaign of missions for you to explore. You will need to create a second campaign (in the menu) and select Extra Missions from the dropdown box (SWAT4 + TSS are selected by default). The Meat Barn Restaurant is the first mission to be unlocked.
- CO-OP finally working. We've fixed a great deal of the co-op bugs and can confirm the game works over the network. The Join Game menu option now appears. When ready in CO-OP, you can hit a new NOT READY button to unready yourself. The response interface has been cleaned up. The optiwand is slightly better in laggy situations. Lastly, if you are the only one on a server, all votes will succeed.
- Weight and Bulk System. Two new bars have been added to the equipment screen: Weight and Bulk. Weight indicates how heavy your equipment is, and slows you down. Bulk indicates how large your equipment is, and makes your interactions slower. Your weight is shown ingame on the HUD.
- More Loadout Options. You may now pick how many magazines you want to bring, which affects your weight and bulk. Pistols can now be equipped in primary weapon slots.
- New Ballistics System. Bullets are subject to drag (momentum/damage falloff over distance) and ricochet (bouncing off of hard surfaces). The Less Lethal Shotgun can now kill people at point blank range. Body Armor is much more effective; heavy armor has ceramic plates that may break with usage but otherwise is capable of stopping nearly any projectile in its tracks.
- LEADER THROW commands. You will now see a new set of commands, such as "OPEN, LEADER AND CLEAR." These commands allow you to throw the grenade instead of the AI doing it. (Double entries only require one grenade)
- Other minor features. You can now lock doors with the toolkit. The officer AI is much smarter, and won't form "death funnels" at doors as easily. Gangster AI types will sometimes hold their guns sideways. The console has been improved. An FOV slider and Mouse Smoothing checkbox have been added to the options menus, and a Take Screenshot keybind was added.
The full changelog may be found from this link.