Paint.NET 3.0 was released recently. The main new features:
- Generally improved and cleaner user interface
- Interactive Gradient Tool that makes it very easy to draw and then fine-tune placement and coloring of a gradient.
- User-definable color palette (as opposed to just the color wheel)
- New effects: Clouds, Median, Unfocus, Outline, and an improved Sharpen
- More intuitive and more powerful toolbar
- History files are now compressed to save disk space, reduce disk activity, and improve performance.
- "Merge Down" layer command
- Simple and intuitive tab-based multi-document user interface:
Paint.NET is free and I have used it for more than a year for all my image editing. It is powerful enough to do everything I need, but yet simple to use for someone like me who is not an imaging expert.