I was under the impression that modern monitors used the gun(s) to get all of the sizing correct, and that not much was asked of the display surface anymore so that multiple resolutions could be properly accomodated by a single screen ... the multiscan revolution.
I'm a big trinitron fan myself, and I have not noticed any degradation of overall quality when stretching the display to fit the screen. It's bad enough that a 15" monitor is really 14" but if you leave the gap, it becomes a 13" monitor. Admittedly if you make your screen larger you lose some DPI, but the point is that you have the same number of points, larger, and of proportional clarity to how they were when they were smaller.
I thought Apple was simply leaving the default a little small because ... they buy Sony Trinitron tubes and that's how you set them by default to make sure you can see the whole screen. Buy any monitor, that's just the way they come. If you have to readjust your monitor everytime you reboot however, your monitor isn't remembering things correctly. That could be a warranty kind of issue.
All things being equal, I'm looking forward to abandoning CRT's in general and moving toward a true digital display. ... or better yet, an infinite resolution display done by spinning lasers, along with smoke, magic, and a small piece of David Copperfield in my monitor.