I got my S4, very happy, fast, smooth, no probs. I'd read that a few people had reported lag, but not noticed this.
I then received an update (70mb in size), so I downloaded and installed. Now I have lag city. My S4 is considerably slower. Tapping contacts, messaging, email, camera icon etc. are much, much slow, in fact the whole phone just seems sluggish now.
very disappointed and wish I'd never updated.
My device is stating: I9505XXUAMDM.