The community, myself included, begged One Red Dog to reconsider. No other drum machine app offers the same level of functionality; with Audio Paste for sample importing and full Virtual MIDI. It would have been sorely missed if it permanently removed from iTunes.
Developer Peter Johnson listened! Molten it back on iTunes today, with a new update for improving compatibility with other apps in the background.
If you are unfamiliar with Molten, Helder Music has put together a series of tutorial videos. I've embedded the whole playlist here.