Professional Digital Painter
If you are a digital artist looking for program this is the one that you need. You will be completely surprised at how the program renders art mediums. The watercolor effect looks like real watercolor. The brushes look amazing. You can even change the type of paper. This program is one that still surprises me daily.
Pros
With Painter you can utilize so many other art mediums that you may not have in your studio. For example, you may want to try using oil paint, but it can be expensive and you may not like it. With Painter, you can at least get the same effect, but without the medium.
I do use Photoshop after I finish with Painter. A neat bonus with the program is that it saves your layers and you can open them into Photoshop with all of the layer exposed and treat it like you would in that program. Some times I miss things in Painter which then I can clean up in Photoshop if need be.
Cons
The program itself is very expensive, but at the end of the day, you have so many tools at your expense that you can utilize. If you tend to do add a lot of brushes and/or effects depending on your computer, the program can crash. You just have to be aware of what you're doing.