Suggestions for next controller.

FX 3+4 switch button (like the deck A/C+B/D buttons).

Replacable faders and crossfaders.

Scratch wheel disable button...so that no touch will scratch, only jog.

Tempo fader disable buton...too easy to knock tempo fader and ruin a mix.

FX buttons closer to faders (things get confusing when mixing four decks with FX)

Filter on/off button (above headphone cue, i have remapped headphone cue to filter on/off...i use this more than the headphone cue buttons...i rarely switch headphone cue when using SYNC)

CUP button instead of SYNC at the bottom....SYNC would be better below the headphone cue button)

Support for draggng and dropping files from iTunes to Traktor on Mac. On my PC i can use two screens, so i can browse files and make custom playlists on my laptop screen with iTunes while having FX and four decks on an external monnitor positioned in front of my S4. I can't drag files from iTunes into Traktor on my Macbook. Rubbish. I now have to use the dreadful 'browse' button mid mix, or rely on two lines of file browser.

Better still...multi screen support!

Endless pots with led markers for FX channels...each time i change an effect i have to move all the knobs, or i get some horrible sounds...if the screen knobs change, there should be a function to auto map those changes onto endless pots, like the Novation nocturn. I have ordered one of these so i can map FX 1+2 and the FX buttons away from their current position down to the bottom edge of the controller, and leave the S4 FX controls for FX 3+4.

thats just off the top of my head.

if i come across any more issues/suggestions i'll be sure to let you know.