The finger drums are intuitive to play and setup/modification is easy enough (plus there are plenty of youtube tutorials for this unit).
The design of the drum pads are excellent and this makes playing drums as intuitive as typing on a keyboard, and I've been able to achieve more realistic sounding results far more quickly with this than I have using grid-based trigger pads or manual programming.
This said, some elements of the unit are a little clunky/dated feeling, such as the process for loading your own samples or the necessity of using a USB drive to record, but I see these more as quirks of the device than real detractions from it's usability.
My only real criticism is that when programming a custom kit, the device has no RAM so if you accidentally change patches without saving first (as is quite easy to do) you'll lose everything you've programmed. The only way around this is to remember to save every single time you change a parameter on a custom kit, which makes the process very slow and quite tedious.
What this could really benefit from would be some software to support custom kit design and loading samples. Perhaps this is something that Yamaha could produce in the future and add support through a firmware update.