The paid version is definitely worth more than the $19.95 it costs. It gives layers with Photoshop layer blend modes, import/export of layered Photoshop documents, much more control over the tools, reference images pinned to the canvas, and way too many things to mention.
ArtRage works well on high-resolution systems. I'm running it here on a 2560 x 1600 monitor.
If you feel the UI is getting in your way, you can dismiss and restore it with the <tab> key or with a right-click. The drawing area is designed to be huge and in your face - ArtRage is all about getting into a creative mindset and not be distracted by technical controls. You can use the zoom, pan, and rotate tools on the preview pan to shrink and reposition your canvas to a more comfortable position that suits you better.
ArtRage is not supposed to be a Photoshop replacement. Photoshop is a technical application for precise layout and photo-editing. ArtRage is about the chaotic process of being artistic.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"