Firmware has usually gone through the paces and I wouldn't worry about issues. Having said that, I didn't update my 7d until I sold it. Seems like the clean hdmi out and f8 focus was the main concern for the 5d3. If you're okay with not having those and taking a chance on the "phenomenon" junk, you could pass. It really isn't hard to update if you wanted to. Copy some files to a flash card and find the firmware number in the menu. Just make sure your battery is charged.