Paint.NET , is a typical Java applet or application written in .NET managed code with mostly C# and some C++ . With around RAM usage - 60 MB , this GIMP alternative is fairly impressive.
Paint.NET loads much faster than GIMP or Photoshop , though it does not contain all the features of GIMP but it is fairly good application, the User Interface is inconsistent with the Windows desktop and feels alien to a Windows user. It offers an extremely intuitive and usable user interface with the transparent toolbars . It is currently maintained as an Open Source project by some of the WSU alumni who started the project and some of them joined Microsoft this year.
Paint.NET 2.5 currently only runs on .NET framework 1.1 but Paint.NET 2.6 will be released some time in January which will run on .NET framework 2.0 and promises to be even more optimized.