The main drawback of this software is its CPU requirements. I have a i7 3770 and it "cracks" on Reaper. The strange thing is that it works quite well in Reason. I guess it's a problem with multi-core handling.
Other than that, I would like to send a different MIDI sequence to each SEM separately but its is not possible. What is possible is to split the note range eigth times but you ends up with transposition problems.
The sound is quite good and the features need some time to explore (what I didn't really achieve at this time).
I like to run a little sequence on some SEMs and play with the others.
Actually it's not a "must have" but for the price it's fun to use. I could not use it in a song due to CPU requirements without freezing tracks.