After spending the first 8 years of my life as a music producer locked inside the computer, I felt like I needed something to spice up my workflow in preparation for my next album. And... that album is finished now, and all of the songs were written on this little unit.
It is very inspiring to use, and I can get lost in it for hours. The workflow is obviously based off of samples, so if you're dependent on using MIDI and synths in your music, this unit is not for you.
There are two things that bug me about the 404 mk2.
1. It doesn't have any live looping functionality, which would be priceless for live performance as well as producing music faster.
2. When I first got my unit, the pads where a bit glitchy and when they were hit they would sometimes double-trigger or triple-trigger. Though it seems like that problem has gone away with time, as I've used the unit more and the pads have gotten time to settle in.
If you produce pop, hiphop and house, this is a no-brainer.