Is that a click-bait title?!
I don't think so. While Raspberry Pis were doing well over the years. There never was an attempt to creating a breakthrough by the RPi-foundation. At least that's my thought on things.
Personally, I was never really attracted to their devices, until the RPi3B+ was released. Now we are talking. Not perfect yet, however, the device was boot-able over USB and with 1GB of RAM, this has beaten many of my previous Linux machines.
With the RPi 4 coming in, the game changed. Now we are talking about a tiny computer that boots from USB3, adding the speed needed for real computing.
In fact, I used a RPi4-8GB in a 64bit computing environment successfully.
The before mentioned setup required some pain and suffering to set up, in particular choosing the 64bit OS that supports the 8GB. So, is that what I would recommend to others? No it is not, only if you know your ways around Linux and stuff. Many of the amenities you get with a 32bit Raspberry Pi OS wont be there. Lets wait and see how the 64bit Raspberry Pi OS will perform, once it left the beta stage.
So, what the fuzz about the RPi 400 then? Well, it is not much of an improvement over the RPi4 to be honest. However, having the only choice of a 4GB version eliminates the need for a 64bit OS. Consequently, the Raspberry Pi OS is all you might want to use.
And that is what I am running on my machine, which I actually use for business, believe it or not. I wished the keyboard was a little bit better, but for the rest, the RPi 400 does a fine job.
To add something technical here, I did overclock my RPi 400 to 2.1GHz by adding the following lines to the file /boot/config.txt (I left the original comment line for reference):
#uncomment to overclock the arm. 700 MHz is the default.
over_voltage=6
arm_freq=2100
gpu_freq=750