I've seen some illustrators use a combination of Corel Painter and Photoshop with exceptional skill, so I downloaded a free trial of Corel to see if I could incorporate its tools in a similar way. I proceeded to make a little sketch to test out the brushes and their various "sliders".
There are some things that I like and things that I don't like. Of the few weaknesses in the program, I think there are some that I can get used to. For example, increasing and decreasing the brush size takes forever when using the shortcut keys, so I found it easier to go up to the size slider and drag it. Now, the good thing about the added hurdle to changing brush size is that it forces me to continue painting with the same size brush. This is a good thing if you are going for an effect with expressive brush strokes. One thing that is less beneficial are phantom brush strokes that appear out of nowhere while you're painting. Not the end of the world, but they can be annoying, especially if you don't notice them until later.
The strength of the program as many know is its ability to simulate traditional media. For me, it's not so much it looking like traditional media as behaving like traditional media that I enjoy. I love the way the oil brush settings smear your previous brush strokes with each new stroke, preventing the straight-edged overlaps you often see in digital paintings made with Photoshop.