Well there's a few [very] small features left to go for the 3.0 release, and the beta should be out within a week or so. Please note that with the beta release v3.0 is considered "feature complete." This means there will be no more added features. The remaining time until the February release will be spent on bug fixing, stabilization, and something else I'm hoping to announce soon enough.
* Edit -> Fill Selection. Every once in awhile, while using Paint.NET, I get the sudden urge to need a feature like this. I've selected an area and I want to fill it without having to, 1) switch to paint bucket, 2) set tolerance to 100%, 3) shift+click. Now I can just hit backspace.
* Hotkey adjustment of brush size. Everyone's always asking me for this and it make sense to add it. Now you can click the + or - in the toolbar or use [ and ], or Ctrl+[ and Ctrl+] to go in steps of 5.
* And ok you guys strong-armed me. Right-click on the color swatch will set the secondary color. But only in the swatch, not the color wheel.