Kontakt, as I'm sure you all know by now, is Native Instruments' flagship software sampler, and, as the large number four above suggests, it has now reached its fourth version.
Note the Dynamic keyswitches (blue) and the Standard keyswitches (pink) on the keyboard. Kontakt's rack view, showing the library browser (left) and an Orchestral instrument loaded. It's got a bigger sample library and some whizzy new features, but what Kontakt 4 really wants to do is make your life easier.