Usually, at lower resolutions the differences between image quality are not very noticeable. Only at the higher resolutions do the good and video cards distinguish themselves. The Matrox Millennium G400 is aided by its 300MHz ramdac, but also by its tradition and proven track record for 2D image quality. If you only have a 15 inch monitor, however, you probably won't be able to take advantage of the Matrox. In terms of the image drivers, the Matrox allows a great amount of control and manipulation.
Refresh rates are adjustable in one hertz increments.
This allows you to take maximum advantage of your monitor. Adjusting the size and geometry of the image is also possible through the drivers. Most importantly, changes to the desktop color depth or resolution were executed flawlessly, showing a very stable image driver. There is nothing more annoying that having your computer crash when you are switching between 16bit and 32bit color. With Matrox's Millenium G400, I don't think this will be a problem.