Every TFT I have seen in my life had a native resolution, and not running it at that resolution gives u a serious loss in text etc viewing quality, it does not matter for movies/games though.
Also, I have never seen a TFT with native resolution lower than the maximum supported resolution, the TFT's do support resolutions lower than the native resolution but they are not meant to be set at that resolution 24/7, the quality is just awful. All the Viewsonic monitors in question have a native resolution of 1440x900, if u own one of them, and u are not running it at 1440x900, a message will pop up saying "For best picture quality please set resolution to 1440x900".