This was also a concern when I switched from a DS to K-r. I did not miss the top LCD though. It really wasn't useful in dim light due to the lack of illumination anyway.
It was actually more natural to view the rear LCD, imagine playing PSP, Gameboy, or any of those handheld gaming consoles with the LCD on top of the unit
.
As mentioned above, it has an advantage when the body is below eye level like when using a tripod.
Also, shooting in dark conditions (think sunrise) is not ideal with a bright LCD in front of your eye. Yes you can turn it off, with several button presses on a K-30, but it would have been better with an eye sensor. But then again, in this scenario the DS' top LCD is useless without light