Nope, it has nothing to do with the resolution being set below the "native res". As far as the cleartype issue is concerned, I always felt that screens looked better with it turned off. I don't know why, its just a personal preference(and yes I've used the cleartype tuning application that you download off of Microsoft's website). And yes, the screens were all turned up to their maximum brightness.
Its a very subtle issue and I'm pretty sure that most people wouldn't notice it but I do. Asking the salesrep certainly wouldn't help considering that most of the time, they know almost nothing about computers. I also noticed that this issue exists with the Dell e1405 but absent from their other models...it actually extends to more than the text, it seems that the screen overall is less "colorful" is the best way I can describe it. Its as if someone added a shade of white to all the colors so it becomes slightly fainter and not as crisp...