For various reasons, I end up doing a lot of Image Manipulation in my various programs (Mainly scaling, mind you) and I have to say how much I like System.Drawing. I'm currently polishing off a Solitare program, and adding the ability to customize cards & the background of the playing field, and after a little judicious refactoring, it took about 20 lines of code to load, scale, update, and draw the new images. With no real noticable difference in drawing speed. Great!
My only real complaint is that you can convert a bmp to an icon (at least, I can't) and it can take ungodly amounts of memory depending on the size of the image (I have a program that can put separate images on a multi-monitor system, and it takes something like 100+MB to create a 3 monitor image. Yikes!) Fortunately, it can release that memory as soon as it's done, but still!