It is excellent of course for real media painting however for creative freedom you should check out Zbrush.
It may appear to be a 3D app, and it is although it is not like the others. But you can forget all about the 3D bit and use it for its completely mind bending 2.5D tools.
That means that impasto doesn't have faux depth but real depth, with real lighting which can always be altered. Here's an image from an artist who only uses the 2 and 2.5D paint tools. Check out the featured gallery thumbnail at the top of the page
Even a 3D novice can sculpt easily just like as if you were using clay and then texture it in real time. You can even texture it using Painter without leaving Zbrush thanks to their new free ZAppLink plug.
It's free to download the demo and you can keep renewing the demo license for as long as you like.
Studio Artist from Synthetik Software also looks like fun but I've only played with it.