The fact that the casing feels cooler could actually mean that it has worse cooling. The casing would naturally be a pretty good heatsink, with decent thermal mass, pretty good surface area, and with the relatively good thermal conductivity of aluminum. Heat transfer is best done by direct conduction, not by radiation or convection. So the cooling might then actually be best if the processor and all the parts that give off a lot of heat had a direct thermal path to the housing. This would then mean that the unibody casing would feel much warmer/hotter, while the precious internals of the computer would be much cooler as the heat could transfer away better/faster. If the unibody casing does indeed typically feel cooler, this could actually be a result of the internals being thermally insulated, and actually having a lot of heat trapped inside them. This could then actually be a step in the wrong direction.
Stating hopeful-at-best possibilities as fact = fail.
Not entirely true.
The newer Unibody systems have a different style for heat dissipation. On the older generation, the discrete models, the heatsink actually creates a non electro-conduct to the bottom of the casing. Thats why the discrete models were extremely hot, especially on the bottom to touch. This required both the heatsink and the entire casing to radiate heat away from the source.
The unibody systems have their heatsinks no where touching the bottom of the casing. However, in theory it shouldn't touch anything at all, but it does. It touches the keyboard. This is why you'll feel heat on the keys. The casing itself, does get warm, but does not get insanely hot because theres no direct contact, only passive contact (via surrounding air). Now the only way to escape the heat in the new unibody is via the rear vent. This large vent does have some advantages. The vent here is slightly larger and less restrictive then the older discrete models. The older models had less area for air to enter or exit. However, the older models had the ability for passive (casing) cooling while the new ones don't.
Whether or not the new Unibody runs cooler with this design is up for debate due to the fact technologies change with each revision and newer tech runs cooler then older tech.
