If I were to pick any midi controller in my setup that I could never do without; This would be it. You can't really beat a well built controller with a 4 piece drum sequencer built in. The lights are bright and lovely. the knobs feel great and respond like butter.
One of the most versatile MIDI controllers I've ever had. 64 buttons and 64 buttons in a small package thanks to it's virtual banks and it can be expanded even further with clever mapping!
This just saves me from carrying my Maschine, I can just load one-shot samples created in Maschine into Traktor and sequence them in a remix track... I also use it for Instant Gratification FXs.