I have had this phone now for over a week and am absolutely delighted.
A couple of days ago I started using Touch wiz again and reset all the preferences on my apps thus having them all installed and not disabled. I didn't find a lot of lag, and TBH, the place where I found it most was when opening the gallery, gotta admit, its there, not a deal breaker and not worth the hair pulling and wringing of hands that some seem to suffer, it is a slight lag but nothing that would cause me worry. Other than that, it seems quite smooth to me. IMHO, the lag is overplayed.
I find that I like Nova prime, it just seems to be made for this phone and have reinstalled it. Battery on mine lasts me really well, ATM I have 41% remaining after taking it of charge 23h 28m 41s ago with an on screen time of 2h 49m, my screen is on full and all the bells and whistles are active, blue tooth etc.
I think it feels quite nice in the hand and has a premium feel, it doesn't bend or creak and find that I prefer it to the S3 (I hve owned one), IMHO, the build quality has been taken up a notch.
I do think that the screen is not the best in the business when viewed outside in sunlight, but for me it is liveable, inside (Where most of my use is) though, the screen is gorgeous, I like it, but others that dislike saturated colours may not like it as much.
I enjoy this phone better than any of the phones I have had previously owned. In fact, I love this phone.