After the WDTV is powered down, the hard disk remains on, causing the device to get very hot. I have the latest firmware (1.07.18). The same hard drive works perfectly fine on the older generation WDTV Live (no wireless) and powers down correctly when the device is turned off. On the WDTV SMP however, the light stays on, the disks are still spinning even an hour after the WDTV turned off.
Hard drive is Seagate freeagent goflex 1.5tb (STAA1500100)