Seems like all the Smartphone makers have been trying to re-invent the wheel by offering new phone designs. By now, end users most likely have strong preferences to the layout they want to use, whether it be the brick like the Treo 600/650/700 or the clamshell like the Kyocera 7135 or Samsung i500/i550, or the new slider styles that are being made by Audiovox, Samsung, LG and others. So what do you prefer?
Personally, I go for the clamshell because it hides/protects the massive PDA screen, which also has the benefit of being stealthy: information thieves are more likely to overlook a clamshell because it doesn't have that "PDA look."