Just to clarify, Dingo has a "Sleep" mode and not "Hibernate".

The Marvell CPU used by the eDGes has multiple power saving levels, each of which requires special driver code to be supplied by Marvell for use by companies using the chip. Since the chip was new when the EE was released, the driver did not yet exist. Last summer Marvell delivered the necessary driver to enTourage which proceeded to add a "sleep" mode to the EE.

"Sleep" is a moderate power saving level where the CPU remains active, and indeed the wifi. The LCD turns off, though. As a result, there are some power savings, but the battery drains steadily. When the PE shipped, it got the same power saving "sleep" mode.

"Hibernate" is typically a zero power mode where the CPU, and all other circuits, are turned off after saving RAM contents to hard disk or flash RAM.

With Ermine, enTourage has encorporated a new "hibernate" driver from Marvel that appears to only actually be effective on the PE, where it does seem to be a true zero power mode - the wifi turns off and the PE will not check email, etc., while closed. I suspect the EE either didn't get a real hibernate mode at all, or the driver is quite buggy (I would have thought both devices used the same CPU, but since the behaviour is different, and since enTourage never actually published the PE CPU specs, we don't really know).

When you downgrade to Dingo, you should lose all indications of a hibernate mode. Closing the EE or PE should cause the LCD screen to go dark, but you won't see the "your device is hibernating" message on the eInk side.

This implies that all wake-up issues (WSOD, won't wake up) should go away after the downgrade. However, there's a small chance that Ermine actually updated the CPU microcode and/or some system flash ROM that isn't reversed by the downgrade. If the update made to the microcode or ROM was buggy, then it may be permanent until (and if) enTourage releases another update.