Is it possible to set independent lengths per channel on the step editor?
Fx: channel 1 is 16 steps long, channel 2 is 7 steps long, channel 3 is 5 steps?

Or is it a considered feature?

No, it is not possible. But it is a fun idea.

So fun as to implement it?

I do it in Reason, with the DrumSequencer patched into uTonic. Makes uTonic even more fun than it already is.

I'm just evaluating Microtonic. The first thing I am wondering about is the poly-rhythm possibilities. If it's not a feature, can individual instruments/tracks be triggered separately?

For those on Ableton Live with M4L, there's a pack for sale by SkinnerBox called Time and Timbre that contains a very flexible sequencer module they call Time. You can set both the duration and devision of each of 6 tracks out to a Live drum machine or VST.

If Microtonic can listen on different MIDI channels (or pitches,) maybe the poly-rhythm can be driven externally? If this is an obvious done thing, I haven't gotten through the Manual yet. Apologies.

Glad to gave found this thread. I so love Microtonic, and I love polyrhythms. And this plugin is SO worth to be taken care of. So count me in: Polyrhythms, pretty please! :D

All 8 channels of Microtonic are assigned to different midi notes, so using an external sequencer is not a problem.