I got myself a S4 to replace my aging HTC Desire, the S4 hardware is great, but software is cluttered so may try a 'Google Edition' rom in the future.
Until then, here are some of the changes I made to make the experience better:

– In Sounds, turn off Touch and Dialling pad sounds, enable vibrate when ringing.
( Too many annoying sounds, the whistle notification being the worst. )

– Enabled developer options, set 'Window, Transition, Animator' scale to off.
( Makes navigating and accessing menus in TouchWiz feel more snappy. )

– Ran S-Voice, settings, unticked open via the home key.
( Removes delay when pressing the home key. )

– Play Store, installed 'Google keyboard', in its settings, set 'Voice input key' to off.
( Better keyboard, and you get a comma key when voice button is off. )

– Application Manager, All, Disabled 'PageBuddyNotiSvc'.
( Gets rid of the 'Recommended Shortcuts' from the tray, since you cannot customize them. )

– Installed 'QuickPic'. Don't disable stock 'Gallery' or camera app freezes after taking a shot.
( Allows you to exclude folders, so that you don't have a gallery of music album art. )