Re: What usage ?
Some people seem to actively like onscreen keyboards. You can get reasonably fast with them now, so long as you're willing to put up with some errors and then fix them in the text later. Which brings into play the clumsy poking at screen trying to get tablet to insert the cursor in the right place - something else a stylus is perfect at. Although on Android you have the option of Swype, which I've never had the chance to try sadly.
Others prefer the Blackberry style keyboards, which I dislike even more than touchscreen ones, as I have big hands. I guess in my case, it's because I'm a touch typist, so something that looks like a keyboard but I can only 1 or 2 finger type on annoys me. Whereas handwriting recognition is nearly up to full writing speed.
I found, in my tablet PC days, that the sylus was a natural fit in my right hand, between index and middle finger (and base of thumb), leaving my middle finger and thumb free to poke at the screen and do the odd gestures. That was partly the limitations of the old style resistive screens and Vista tablet edition, but mostly I could run it perfectly well on finger alone (until diving into weird settings menus) and the stylus was there because it was comfortable, and instantly available for writing.
There's a lot of ways of pushing notes you've taken through OCR - after you've taken out any diagrams you may have put in at the time. Which means you don't have to faff around in the meeting with concentrating on anything other than getting your notes down and the meeting. And of course, all your meeting notes are now automatically filed in date order - even if you haven't got round to naming the files.
Obviously sketching is one of the perfect uses of a stylus. My friend with his sketching on photos came up because I asked him to build a big corner cupboard for me. Because he was at mine for dinner, and we were discussing design, as well as talking about normal stuff, he rushed his measurements. So I got a call later, and had to do some of the measuring up myself. Whereas he now takes a photo when on site and sketches all dimensions on it, so he can instantly see if he's forgotten anything. Plus the workshop have a photo to consult when it comes to queries when building.
The reason I thought of all this is that we were talking yesterday. He told me that his clients are quite impressed with the shiny Galaxy Note 2 - as most haven't seen a phone that can do this stuff. He said, "they're mostly richer, brighter and have more gadgets than me". I should have commented at the time that I was one of his clients this year, so thankyouverymuch... Anyway yesterday he was with a client, and while she was making a cup of tea, he measured and sketched, took a photo of the antique handle on some piece of her furniture, and was able to send that off to his PA with notes scrawled on it, and by the time the client walked in with the tea, his PA had emailed him back a couple of matching options from their suppliers' catalogues. So he was able to turn to the client and show her the shinies available while discussing design options. This is obviously excellent for impressing clients - and that's probably half of the sale. The fact that he can sketch in 3D and upside down, while explaining a design idea to you is also pretty impressive...
But for a technophobe who struggles with all things computer - and couldn't even set up an iPhone - it's all worked rather well. And I suspect that sketching with a stylus comes more naturally.