In this overview, we have collected all the details about Apple TV that have emerged after the event yesterday. Siri, for example, will only work in 8 countries at launch, WiFi is faster than a wired connection, Apple TV will work with game controllers, 200MB is the maximum for apps/games, and much more.

The small print
We will update the list as we learn more. Feel free to contribute.

The box
Apple TV runs tvOS – a new operating system for the TV
Apple TV has 2GB RAM
It supports the new WiFi ac standard, which also means that WiFi in Apple TV is now faster than ethernet (up to 1000 Mbps)
Apple TV measures 98 x 33 x 98mm – 10 millimeter higher than the old one. It weighs 425g (old one: 272g)
It runs the A8 processor and a PowerVR GX6450 GPU
Bluetooth is version 4.0 – the same as before
Some argue that the HDMI 1.4 port in the new Apple TV theoretically supports 4K, which is true, but in practice it would also require HDCP 2.2 and HEVC or VP9 to make 4K video possible
There is an USB-C port (the reversible USB kind) in Apple TV, men it seems that it is only there for diagnostics purposes
The old Apple TV box will not get tvOS
There is - obviously - no TV tuners in the new Apple TV

Picture & sound
No 4K support in video/games and no HEVC support
The new Apple TV has no optical audio port
Audio support up to 7.1 Dolby Digital Plus and lossless formats. But no support for HD audio from DTS and Dolby
Audio from movies and games can be transmitted wirelessly to Airplay speakers
The box has an "Enhanced Speech" function to reduce background audio and make speech clearer. It is designed for night time viewing. Enhanced Speech can also be activated with Siri

Siri, Remote & apps
Siri on Apple TV works in only 8 countries at the moment (Australia, Canada, France, Germany, Japan, Spain, the UK & the US)
Apple TV will launch in 80 countries in late October – the full list is not available yet 
Markets without Siri support can reportedly use text input from a iPhone or iPad
The new Siri Remote has glass at the top – and a physical click
The same remote control will be available in all countries but Apple will only refer to it as the "Siri Remote" in supported markets
The touch pad on Siri Remote has three "click" levels. A light tap lets you preview the app, a click opens the app and a long press lets you re-organize apps.
The Siri Remote can work with older Apple TV
The Apple TV comes with Lightning to USB-C cable for recharging Siri Remote
There is IR in the box and remote (for volume control of TV) but the box and remote will primarily use bluetooth
Confirmed apps include; iTunes, iCloud, Netflix, HBO Now, Hulu, Showtime, MLB, NBA, NHL, CNN, FOX, PBS Kids, ABC News, Disney Channel, ESPN
Siri & universal search works – so far – with iTunes, Netflix, Hulu, Showtime & HBO
Siri can be used to fast forward or rewind with commands such as "jump forward 10 minutes"
If you ask Siri to "Find action movies" you can filter your search by adding "only the new ones" or "only ones with Jason Bourne"
You can ask Siri questions such as "Who directed this movie?" or "Who plays the main character"
Apple Music will be available on the new and old Apple TV
Plex is working on an app for Apple TV
VLC is working on an app; "It’s very early though, but we have video playback!"
Infuse (FireCore) is also coming
App Store for Apple TV is not yet live – but will most likely be at launch
You can re-organize app icons
Apps & spil cannot come in higher at 200MB for app install files. Additional content will have to be downloaded or streamed on-demand as "tags" (packages)
Games are not allowed to store "saves" directly on Apple TV. It must be saved in iCloud
A fast internet connection without a max cap is required since the box will download and stream content on the fly during use
The box supports iCloud Photos
iTunes Home Sharing is supported

Games
Confirmed games include; Asphalt Airborne 8, Disney Infinity 3, Rayman Adventures, Crossy Road, Beat Sports, Shadowmatic, a, Fantastic Plastic Squad
If you already own a game on iPhone/iPad you also own the game on Apple TV
Apple TV has support for true game controllers (via bluetooth). Developers can decide to support them or not
Game controllers for iOS include; MadCatz, Steelseries, Logitech & Razer
The first official game controller for Apple TV is the SteelSeries Nimbus, which looks like a typical game controller. It can be charged via a Lightning port and has 40 hours of battery life. It will cost $49 dollars.
You can pair only one Siri Remote to the box but several iPhones/iPods & game controllers

User interface
The ”top shelf” content bar at the top (the one used for iTunes movies/series) can be customized. You can include content from other services.
When using the touchpad remote you will see app icons started to shake just before you move to the next. This feedback will make it easier to navigate with the touch pad
Apple is using a"multitasking bar" at the bottom of the screen when Siri is activated. You can also bring up the menu by double-tapping the Menu button
Apple TV can obviously communicate with iPhone/iPad and Apple Watch, but you can also get things like your heart rate on the TV screen, measured by your Apple Watch. This is useful while using fitness apps on the big screen
Apple has shot moving screensavers that take the time of the day into account for day/night shots
Airplay is still included and is using overhauled protocols for faster operation
Apple did not talk about Homekit integration but it appears to be part of the new Apple TV.

Learn more about the new Apple TV here, where we will include everything we know.

- Source: Apple, 9to5Mac, The Verge, Variety, Plex, AppleInsider, Engadget, Engadget, iMore