The S pen truly is pivotal to the Samsung Galaxy Note 8.0 experience. First introduced with the Galaxy Note, it has a vast array of special features that are a great improvement over what can be done with just your fingertips.
We already covered the contextual page, which comes up automatically when you pull out the S Pen. It's only visible when the stylus is out and its icon is a little pencil, while regular homescreens are still indicated by dots.
Anyway, there's another way to launch apps - with gestures. You press the S Pen button and swipe up to access Quick command. Here you can draw a "@" sign to launch email, "?" to do a quick search, "!" to launch Maps, among others. Besides the symbol you can add a keyword - what to search for with the "?" or define search range for the "@": recipient, message body or both.
You can add new commands too - just pick a function (e.g. enable Bluetooth, there's a long list to choose from) and write on the symbol you want to associate with it.
You can also hover the S Pen over various things to get a better look at - expand S Planner events, preview emails and text, preview videos and even a point on the video timeline.
The S Pen also lets you quickly snap a portion of the screen and use it in an app - email, S Note, etc. Speaking of S Note, you can launch it by double tapping with the S Pen while holding down its button.
Samsung came out with S Voice as an answer to Apple's Siri before Google came out with its own solution in Google Now. S Voice is the culmination of Samsung's ongoing effort at integrating voice commands, which began with Vlingo back in the day - you may remember the voice activation (saying "Hi Galaxy" to trigger S Voice).
S Voice can do the usual - search the web, make calls, send texts (which Android natively supports and so does Vlingo), but you can also use it instead of notification area toggles, to answer or reject incoming calls, start the camera and take a photo, and control the music player and stop or snooze alarms.
It's also a tool for quickly looking up facts - it's powered by Wolfram Alpha (which handles some of Siri's answers too). It has an enormous database covering topics ranging from Culture and Media to Physics. S Voice can also be used as a calculator.
Samsung has decided to keep S Voice alongside Google's solution as the two do differ in functionality. Jelly Bean has the unspoken Google Now info cards, but it also features Google's Knowledge Graph, which can answer factual questions.
Google Voice Actions can handle stuff like sending messages (SMS or email), initiating a voice call, asking for directions, taking a note or opening a site. It can't, however, toggle Wi-Fi or control the camera, among other things that S Voice can do. At least not yet.
One big advantage of Google's Jelly Bean is that the voice typing functionality doesn't require an internet connection to work. You can enter text by speaking anywhere you can use the on-screen keyboard - be it the Messaging app or a note taking app - without the need for a data connection as long as you have pre-downloaded the needed language packs (and those only take about 20-25MB of your storage per pack).
Making voice typing available offline also made it faster as it's not dependent on your connection. What's even more impressive is that the transition hasn't cost it anything in terms of accuracy.