People are confusing types of upgrades here. Motherboard firmware and camera firmware work for an analogy, Virus updates, video drivers and the like are not the same type of upgrade. There is also a difference in how firmware updates are 'pushed' for different kinds of hardware. I work with some hardware that in order to work with newer hardware (memory, CPU's, those kinds of thing) not upgrading firmware simply isnt an option.
What would be nice (some motherboard manufacturers are doing it now) is making a copy of the working firmware to a seperate/backup eeprom so if one goes kerplunk you can continue to work off the old one and keep going. In general though, the firmware *itself* has never been the issue with cameras, unlike secondary issues with computer hardware. Its losing power while doing the upgrade that is the potential killer. When you take this into consideration, assuming one can read instructions and has decent power there isn't much danger in updating firmware.
I for one was happy to have my XT have an issue with reviewing images on the LCD fixed with the last XT update, but if I hadn't been in need of that fix I probably wouldn't have been that concerned about the firmware update.
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