I started my second multichannel Hively project, and I have to share my thoughts with you. I usualy write AHX files and composing process is OK. But when it comes to > 4 channels...
1. Space. While 4ch is no problem, moving through 16 channels when only 6 are visible at once is pain in the ass. You could easily fit more channels if the window was resizable. Larger window could have more channels in pattern editor, position editor, more space for instrument list etc..
2. Clone Pattern (position) function. I often make little changes to each pattern to add a little variety to the composition. Each time I want to do this I have to copy & paste each channel to a new one manually. Again, 4ch is bearable, but copying 16 channels each time is frustrating. This simple option would be a huge time-saver. Simply get the data from a specified position, look for new empty channels and copy it there. You can find this function i.e. in FamiTracker.
3. Slider/Arrows in instrument table. Sometimes I write tunes on my netbook. It doesnt have numeric keyboard. It doesnt have mouse with wheel. Therefore there is no way to select 9+ instrument from the list except switching to the instrument editor. Annoying :)
I hope you'll find my suggestions worthy considering :)
Ps. We are talking Windows port here of course.