My friend has one and he loves it. The tech level is phenomenal. The screen can actually sense your finger from almost a centimetre away from it, with pinpoint accuracy. Magic.
I've got it. I can't think of any flaws besides being a bit big (this only slightly affects being able to pull down the menu from the top with my thumb). It's really a fantastic phone.
I only have the Nexus 4, but I have a few friends with S4's that absolutely love them. I would get one too if I didn't just get this one 8 months ago...