A lot of people have been waiting a long time for this. If the firmware update doesn't address the very noisy Seagate issue there is something almost mockingly cruel about this update and lends credence to the idea that it isn't just a noisy hard drive problem but a much more expensive logic board problem, too, possibly requiring both be changed at the time of repair; the number of incidences where people have had the hard drive replaced with one just as noisy, multiple times, causing them to give in, is disheartening. Anyone with said problem will very likely find that the hard drive itself passes all tests throw at it, including Seagates own (free) SeaTools diagnostic.
Having just made an unhelpfully negative statement, I will bolt on a question. For an end user to swap out the hard drive for a quiet one is inadvisable because a) the screen has fragile ribbon cables, etc, and if you reassemble your iMac and it doesn't work... and b) Apple flash the firmware of their hard drives so replacing a Seagate 1tb with an identical drive without said Apple firmware causes the hard drive fan to spin up to almost maximum speed. There are workarounds but none of them very elegant. So my question would be, has anyone bought themselves one of the said Samsungs and the appropriate Samsung temperature cable and tried to flash a vanilla Samsung drive with the Apple firmware? If so, has that turned your iMac from a loud popcorn maker into something semi quiet?