This is a function of the hardware used. I'm not sure how many cell phones use the Marvell chip. If yours uses Snapdragon, its capabilities can be quite different. The software side of it no doubt plays a big part, too.

The Marvell chip used in the eDGe has multiple power saving modes. The only one that's currently implemented by enTourage is more a "sleep" mode, and it appears the CPU is still somewhat active, hence the steady battery drain. A true "hibernate" mode (where the device is zero power but can restore within a few seconds) is something enTourage talked about early in the year that required some driver updates from Marvell (the CPU manufacturer). A future patch hopefully will roll out this hibernate capability.