I write notes as I'm talking on the phone (another mobile or the landline) to people at work. It's as easy as an ink pen in a paper notebook and I can write finer.
I record critical data like phone numbers using the text function and virtual keyboard.
For google searches the handwriting recognition is good enough even with scrawly letters.
The pen is easier for "clicking" in browser apps like firefox and tables of contents too, which expect you to be using a full sized tablet at least.
I do a few sketches eg size of bookcase, rough sewing patterns, mind maps etc The eraser function is very useful !!
The s Pen is what the Galaxy Note is. I don't think any other manufacturer has one yet. This is why it is not even the same sort of device as the iPad and iPhone, which would both be unuseable for what I do.
ps I bought a spare s Pen from the Samsung Service center in a different colour. Very expensive but I'm stufft if something happens to it. Having a spare means I'll never lose it now. By the way, the "walk away warning" doesn't always work.