On a typical day, lots of general purpose tablet apps in my case...
If in wifi range, I use mine to check email throughout the day, as well as basic calendaring (using Google's calendar app) and task tracking (using Astrid). I haven't warmed up to the Samsung apps yet.
Internet surfing during idle moments. I find the native browser quite usable. This is my 1st 10 inch device, so this is a treat.
On the road, I use an assortment of travel tools. Tripit and FlightTrack to figure out which gate to sprint to next. Weatherbug lets me see the nasty winter weather I managed to dodge (so far). NHL Gamecenter app to watch or at least listen to Bruins games.
Google Play Magazines look really good, and I've moved all my subscriptions off of B&N and onto Google. I was pleased to see they've added Asimov's and Analog, as well as month-to-month subscriptions. Magazines look really good on the 10 inch screen.
Ditto for the Boston Globe app.
A few SGN-specific things I've started with...
I'm spending a lot of time agonizing over whether to use Polaris Office (text editor I can draw in) or Lecture Notes (doodle pad I can insert text in) for taking notes at work. I've used both in meetings already, and am already at the point that I don't take a paper pad into meetings anymore. I'm also torn between soft keyboard and handwritten input.
I've been doing some sketching with Autodesk Sketchbook. I haven't sketched anything in years, so it's fun doing it again.
Way back in high school, I wanted to buy a synthesizer. I still have an old 1979 PAIA catalog that I'd highlighted the unit I wanted in. I stumbled onto the Caustic 2 rackmount synth/sampler app and am wasting a lot of time channeling my inner Brian Eno. (It's probably a good thing I bought a computer instead of the synth.) Not SGN-specific, but the speakers and size help.