I got to try out a W520 recently. It seemed quite nice, and I like machines with a bigger screen but without the numeric keypad (which I generally have no use for). From my point of view, it is a shame the W540 now crams in the numeric keypad. I'd rather have a keyboard with full-sized keys (including shift, control, arrows, etc.) than have the more common cramped style seen with most 15.6" screen laptops.
For all the configurable internal guts and how much people have issues with keyboard layout i wish manufacturers had options for the keyboard on their mid-high tier laptops.
