I purchased the Brushes app about a year ago and found it to be pretty challenging to use (especially when compared with the awesomness that is my little sketch book and watercolor brush/pen)
But I've been traveling this last week and since airport security discourages anything that contains liquids and looks even remotely sharp I found myself with time to kill and a need to draw with SOMETHING -- so my iPhone had to do. These two started to kick open the possibilities of the app.
Not bad, but I'd really like something resembling a stylus (that's not my finger)