I had it as my first drumbox too, but at the time I still had a lot to learn…
Since today I’ve got a nice mk-1 again 
Will probably turn up in one/ a few of my next tracks for Upstairs Underground…
The combination with A4 is brilliant, nice to be able to add filtering over the summed output of the er-1 and to add some (parameter locked-) FX.
Also nice to get the basic drumbits going from A4 (Kick, Snare, HH) and to fill in the rest with the freaky fm-sounds from the er-1.