Anyway, I was unlucky enough to get this particular machine with a faulty fan. It has been reported widely that due to some QC issues at Lenovo or whatnot a number of the laptops (T420/T430 alike) is coming with the fan that has especially maddening pitch at around 3200-3400 rpms. It is one of those sounds that drills your skull and drives you buts in about 17 seconds from the start of it.
If it by itself wasn't bad enough, the BIOS sets the fan to that speed when the temperature is anywhere above like 36 degrees C. If you have the laptop on your laps - that's where you would expect it to have, judging by the name - you're doomed.
There're lots of complains from people about this and attempts to solve it with clumsy scripts written in Python, etc. However, the working solution was under my nose pretty much all that time, waiting for me on Gentoo Wiki.
It also works on Ubuntu 12.04 like a charm. The only modification you need to be aware of on Ubuntu is how to add thinkfan to your machine's startup sequence. You'd need to run
sudo update-rc.d thinkfan defaultsinstead of the the page above suggest. It is so quite here again!
Update: in all fairness, I had to eventually replace the fan, because it was still too noisy in the above speeds, although, it didn't get engage too often. Now, it is completely silent ;)