I'm convinced. I really do enjoy painting on my phone. I can't see how the iPad wouldn't be that much more fun. I seem to loose a bit of perspective with my hand covering a good part of the screen (see different sized limbs below) but all in all I'm quite happy with the experience.
These 3 were all done with ArtStudio. That app is like a mini Photoshop.
I'm also excited to try ProCreate (Thank's for that, Tor). Looks like really nice piece of software that's really thinking about the user experience and is continuing to develop.
Edit: to be clear - the above is a comp of a 2 primed sheets of paper, a pencil sketch and a paint over those. The cool thing is I took them all with the phone's camera, and imported them directly into Art Studio.