Teenage Engineering Rumble Module

As everyone I know, I could not even understand and think what the Rumble Module could really do for the Z. Apparently, this little magic module gives life to the OP-Z and makes it somehow more usable.
It does not shake the desk or anything but only vibrates internally, strong enough for understanding the beat and base as well as the tempo.
I can not say it is vital to have it but once you have it, it is really hard to not use it.
If you have some spare cash, do get it and you will not regret it!