Not a lot of learning curve, just think of a 16 beat pattern and just play!
Part of the joy of making music with "less" is that you can have happy accidents and that sometimes having too many options bog down one's creativity.
This app is a fun throwback to older step sequenced hardware and the UI/etc are intuitive and very well done.
I only recently bought it and have been playing with the synths manually...as if they were the real physical devices. Hence my comment on the steep learning curve. Ya gots to know what all the buttons and knobs do. Or just play with 'em for a while.