[stavros]

I've measured the repeatability on mine, and it was pretty good, though I don't remember the number right now.

The pressure sensor on the hottend is superior to any other method, because it has much better resolution (though maybe not better than the Beacon), and it can adjust to print conditions in real time, which no other start-of-print sensor can do.

[jyxent]

I'm not aware of any hotend sensors doing as you describe. The Prusa MK4 only uses it to generate a bed mesh the same as any other bed-leveling sensors. It does not do any live calibration while printing.

[stavros]

Really? That's very disappointing, if that's the case.

EDIT: I'm not sure, this article says it can detect spaghetti just from the pressure difference, for example:

https://all3dp.com/1/nextruder-prusa-xl-deep-dive/

It also hints at detection of the height while printing.

[jyxent]

Without watching the video referenced in the article, I'm guessing this was based on what they theoretically could do, rather than something that they had actually implemented.

They currently only use the load cells for bed leveling: https://www.youtube.com/watch?v=F7ETSVu04ao&t=940s

I could be wrong, but I would expect that the load cell readings would be far too noisy in order to determine the height of the nozzle while printing. Even if they were accurate, different materials would also behave differently due to different viscosities.

[TaylorAlexander]

To be fair they really shoved the Mk4 out the door (read up on the release schedule for Input Shaping if curious) so there is probably room for development in the firmware. Perhaps they will have live pressure response in a year or two if such a functionality is deemed beneficial.