We've all mentioned this software numerous times but today I finally updated it when it asked me too.
I'm very impressed with the updates. Its now much more responsive feeling(wasn't bad before but its just snappier), it has some more effects and other features. If you don't know what paint.net is then look here:
The only thing I wish it had was a magnetic lasso select tool like photoshop. Once it has that it will be perfect for just about any basic photo editing.
Also version 3 is supposed to be released sometime soon. There are betas out but I haven't tried them.