But out of interest, have you personally ever had any problems with incompatible bootloaders?
Only once - moving from a major point release (7) to another major point release (8). Reloading the v7 firmware to check some things blew things up, so it wasn't possible to go backward. I was committed to v8 code at that point.
The two big concerns we have here are
1) when a user pulls down some firmware that wasn't 'officially' released for the device (e.g., 9.061 on certain units for which we never saw it appear). It can be a one-way ticket if the bootloader that accompanies that firmware isn't compatible with the previous or 'correct' firmware for the device. Rarely, Home causes this. Rarely, we actually recommend it. Sometimes, a user just gets an urge to fiddle that they can't squash.
2) when a user 'upgrades' to new firmware, find that it has dropped functions or added bugs that really foul up their particular use of the device, and would discover that they can't back up. So far, we've been pretty lucky with this since one of the only major reversions we've needed and recommended was for versions after 8.302 (e.g., 8.351) causing problems that sent people back to 8.302 ... and fortunately, there was no compatibility issue raised in that.
What needs to be carefully understood is that the bootloader contains a lot of very low level functionality related to the hardware.
Just noting that it's not
always possible to go backwards, and the article implied that it was. So a user moving 'forward' needs to be aware of the differences and whether it's worth doing before making the jump - just in case it's permanent.