I have been playing PlayStation for years and I never found a problem with the analog stick of the DS3. It was comfortable and I never had any real grip issues. However, with the DS4, my thumbs seem to slip from the sticks. Maybe part of the reason is because I never held the analog stick with the absolute tip of my thumbs.
So how do you guys hold it coming straight from the PS3. Was the transition natural to you? For some reason I can't get used to it, the stick surface area feels too small for me and at times leaves a circular mark on my thumb. Maybe I need to develop a new technique.