Is there any way (like DFU mode) to downgrade to a stable release? I guess there isn't an official way now to downgrade the firmware so maybe it's just a stupid question. I have a test device but if it's stable enough at some point I'll probably want to install it on my main unit.
When the firmware is updated to 3.0, a new version of the baseband is also installed, probably for new bluetooth, mms functionality etc. Whilst you can downgrade the firmware, its no simple task to downgrade the baseband, and not something apple ever allows.
So you probably can downgrade, but will loose phone functionality on an iPhone, and I'm not sure how it would affect an iPod Touch.